Exhaust gas purification device

ABSTRACT

An exhaust gas purification device capable of enhancing handling operability such as maintenance of an engine includes two gas purification bodies which purify exhaust gas discharged from the engine, inner cases in which the gas purification bodies are incorporated, and outer cases in which the inner cases are incorporated. The outer cases are arranged side by side in a moving direction of exhaust gas and connected to each other. One of the adjoining inner cases is inserted into the other inner case to form a double-layer structure. A loosely-fitting gap is formed between an inner side surface of the one inner case and an outer side surface of the other inner case.

This is a Divisional application of U.S. Ser. No. 13/634,121 filed Sep.11, 2012.

BACKGROUND OF THE INVENTION

The present invention of the application relates to an exhaust gaspurification device provided in a diesel engine or the like, and moreparticularly, to an exhaust gas purification device for eliminatingparticulate materials (soot, particulate) and the like included inexhaust gas.

There is a known technique that a diesel particulate filter (DPF,hereinafter) is provided in an exhaust path of a diesel engine (engine,hereinafter) as an exhaust gas purification device, and exhaust gas fromthe engine is purified by the DPF (see Patent Document 1 for example).There is another known technique that an inner case is provided in anouter case to form a double-layer structure in a DPF, and an oxidationcatalyst or a soot filter is incorporated in the inner case (see PatentDocument 2 for example). There is also another technique that a case inwhich an oxidation catalyst is accommodated and another case in which asoot filter is accommodated are connected to each other in a DPF througha bolt-fastened flange such that the cases can be separated from eachother (see Patent Documents 3 and 4 for example).

According to the DPF described in Patent Document 4, to connect, to eachother, an upstream side case of a single-layer structure in which anoxidation catalyst is incorporated and a downstream side case of asingle-layer structure in which a soot filter is incorporated, theupstream side case and the downstream side case are formed intocylindrical shapes having the same diameters, one of the cases isprovided with an diameter-enlarged portion, the other case is tightlyfitted into the diameter-enlarged portion of the one case so that theoxidation catalyst and the soot filter are disposed closely. If thisconfiguration is employed, since a region in the cases between theoxidation catalyst and the soot filter is narrowed (radiating area isnarrowed), there is a merit that probability of temperature reduction ofexhaust gas between the oxidation catalyst and the soot filter can besuppressed.

CITATION LIST

Patent Document 1: Japanese Patent Application Laid-open No. 2004-263593

Patent Document 2: Japanese Patent Application Laid-open No. 2005-194949

Patent Document 3: Japanese Patent Application Laid-open No. 2009-228516

Patent Document 4: Japanese Patent Application Laid-open No. 2009-91982

SUMMARY OF THE INVENTION

According to the configuration of patent document 4, however, when theupstream side case of the single-layer structure in which the oxidationcatalyst is incorporated and the downstream side case of thesingle-layer structure in which the soot filter is incorporated areconnected to each other, since the other case is tightly fitted into thediameter-enlarged portion provided on the one case, both the cases(tightly fitted portions) could possibly integrated due to rust or thelike and cannot be easily separated from each other. Further, since atemperature of outer surfaces of the cases becomes high because exhaustgas passes, a maintenance operation of the DPF must be carried out in astate where the cases are sufficiently cooled, and there is a problemthat handling operability cannot be easily enhanced.

This problem has been studied and it is a first technical object of thepresent invention of the application to provide an improved exhaust gaspurification device.

Engines have high general versatility, and are used in various fieldssuch as construction machinery, agricultural machinery, boats and ships.A mounting space of an engine varies depending upon a machine in whichthe engine is provided but in recent years, the mounting space islimited (narrow) due to requirement of weight reduction and dimensionreduction. Further, in the DPF, it is preferable that the temperature ofexhaust gas which passes through the DPF is high (e.g., 300° C. orhigher) in terms of function. Therefore, there is a requirement formounting the DPF in an engine.

When the DPF is mounted in the engine, it is necessary, depending upon amounting position of the DPF, to elongate or curve an exhaust pipe whichconnects an exhaust manifold and the DPF to each other. However, thelonger the exhaust pipe is, the lower the temperature of exhaust gasbecomes before reaching the DPF, and the DPF's purification performanceof exhaust gas is deteriorated. Further, if the exhaust pipe is curved,since exhaust gas flows therethrough while colliding against the curvedinner surface of the exhaust pipe, the flow velocity of exhaust gas isreduced naturally. If the flow velocity is reduced, the temperature ofexhaust gas is lowered and thus, in this case also, the DPF'spurification performance of exhaust gas is deteriorated.

These circumstances have been studied, and it is a second technicalobject of the invention of the application to provide a DPF of astructure into which exhaust gas can uniformly or equally flow withoutdepending upon a shape of an exhaust pipe.

A technique for mounting a silencer in the DPF is also well known, butif the silencer is merely connected to the DPF of the conventionalstructure, a length of the DPF in a moving direction of exhaust gas iscorrespondingly increased by a length of the silencer, and the DPFcannot be made compact. If the length of the silencer in the movingdirection of exhaust gas is shortened to make the DPF compact, it isdifficult to sufficiently secure the exhaust gas moving distance in thesilencer, and silencing performance could be deteriorated.

Hence, it is a third technical object of the invention of theapplication to provide a compact exhaust gas purification device towhich a silencing function of exhaust gas can be easily added.

A first aspect of the invention provides an exhaust gas purificationdevice including two gas purification bodies for purifying exhaust gasdischarged from an engine, inner cases for incorporating the gaspurification bodies, and outer cases for incorporating the inner cases,the outer cases being arranged side by side in an exhaust gas movingdirection and connected to each other, one of the adjoining inner casesis inserted into the other inner case to form a double-layer structure,and a loosely-fitting gap is formed between an inner side surface of theone inner case and an outer side surface of the other inner case.

According to a second aspect of the invention, in the exhaust gaspurification device of the first aspect, the outer side surfaces of theinner cases are provided with bonding flanges protruding radiallyoutward, one ends of the outer cases in the exhaust gas moving directionare fixed to steps formed on the bonding flanges, and the adjoiningbonding flanges are superposed on each other and detachably connected toeach other.

According to a third aspect of the invention, in the exhaust gaspurification device of the second aspect, the inner case is supported bythe outer case in a state where the inner case is not in direct contactwith the outer case due to existence of the bonding flange.

According to a fourth aspect of the invention, in the exhaust gaspurification device of any one of first to third aspects, an outer sidesurface of one of the adjoining inner cases is provided with a sensorboss body for supporting an exhaust gas sensor, the sensor boss bodyprojects radially outward from a boss body through hole formed in theouter case, and a collar which surrounds the sensor boss body and closesthe boss body through hole is fixed to an outer side surface of the oneinner case.

According to a fifth aspect of the invention, in the exhaust gaspurification device of the fourth aspect, a pipe of a differentialpressure sensor as the exhaust gas sensor is connected to the sensorboss body, and the pipe extends along an outer side surface of the outercase.

According to a sixth aspect of the invention, the exhaust gaspurification device of the first aspect further includes an exhaust gasinlet pipe for exhaust gas from the engine flowing into, and an exhaustgas outlet pipe for exhaust gas passing through the gas purificationbody flowing out, wherein the exhaust gas inlet pipe is mounted on theexhaust gas upstream side outer case such that an exhaust gasintroducing passage is formed by the outer side surface of the exhaustgas upstream side outer case and the inner side surface of the exhaustgas inlet pipe, and at least one of the outer side surface of theexhaust gas upstream side outer case and the inner side surface of theexhaust gas inlet pipe is provided with a rectifier which rectifies aflow of exhaust gas.

According to a seventh aspect of the invention, in the exhaust gaspurification device of the sixth aspect, a flange body which connectsboth the outer cases to each other is deviated from a connectionboundary position of both the gas purification bodies.

According to an eighth aspect of the invention, in the exhaust gaspurification device of the sixth or seventh aspect, the rectifier isprovided on each of the outer side surface of the exhaust gas upstreamside outer case and the inner side surface of the exhaust gas inletpipe, the rectifier of the outer case is located on an exhaust gasupstream side, and the rectifier of the exhaust gas inlet pipe islocated on an exhaust gas downstream side.

According to a ninth aspect of the invention, in the exhaust gaspurification device of any one of sixth to eighth aspects, an exhaustgas inflow opening which is in communication with the exhaust gas inletpipe is formed in the exhaust gas upstream side outer case and the innercase which is incorporated in this outer case, the exhaust gas inflowopening opens in a rectangular shape, and four corners of the exhaustgas inflow opening are formed into are shapes.

According to a tenth aspect of the invention, the exhaust gaspurification device of the first aspect further includes an exhaust gasinlet pipe for exhaust gas from the engine flowing into, and an exhaustgas outlet pipe for exhaust gas passing through the gas purificationbody flowing out, a silencer having the exhaust gas outlet pipe ismounted on the exhaust gas downstream side outer case, an exhaust gasintroducing pipe extending in parallel to the exhaust gas movingdirection is incorporated in the silencer, and an exhaust gas upstreamside of the exhaust gas introducing pipe enters the exhaust gasdownstream side inner case.

According to an eleventh aspect of the invention, in the exhaust gaspurification device of the tenth aspect, a flange body which connectsboth the outer cases to each other is deviated from a connectionboundary position of both the gas purification bodies, and a flange bodywhich connects the exhaust gas downstream side outer case and thesilencer to each other is deviated from a connection boundary positionof the exhaust gas downstream side gas purification body.

According to a twelfth aspect of the invention, in the exhaust gaspurification device of the tenth or eleventh aspect, an exhaust gasupstream side end of the silencer is closed by an inner lid body, theexhaust gas introducing pipe penetrates the inner lid body and entersthe exhaust gas downstream side inner case, and a communication hole fortaking exhaust gas in is formed in a portion of the exhaust gasintroducing pipe located on exhaust gas upstream side of the inner lidbody.

According to a thirteenth aspect of the invention, in the exhaust gaspurification device of any one of the tenth to twelfth aspects, a sensorboss body for supporting an exhaust gas sensor is provided on a portionof an outer peripheral surface of the exhaust gas downstream side innercase which is near a connection boundary position of the gaspurification body such that the sensor boss body penetrates the exhaustgas downstream side outer case, and the sensor boss body is located onan extension of an end surface of the gas purification body whichintersects with the exhaust gas moving direction, and on an extension ofan exhaust gas upstream side end surface of the exhaust gas introducingpipe.

The first aspect of the invention provides an exhaust gas purificationdevice including two gas purification bodies which purify exhaust gasdischarged from an engine, inner cases in which the gas purificationbodies are incorporated, and outer cases in which the inner cases areincorporated, the outer cases being arranged side by side in an exhaustgas moving direction and connected to each other, wherein one of theadjoining inner cases is inserted into the other inner case to form adouble-layer structure, and a loosely-fitting gap is formed between aninner side surface of the one inner case and an outer side surface ofthe other inner case. Therefore, by separating the other inner case fromthe one inner case, the gas purification body in the other inner casecan be largely exposed to outside. Hence, there is an effect that it ispossible to enhance a maintenance operation (such as cleaning of gaspurification bodies) which is carried out by separating the cases fromeach other. Both the inner cases can be easily attached to and detachedfrom each other due to the existence of the loosely-fitting gap betweenboth the inner cases. That is, in the conventional technique in whichboth the inner cases are tightly fitted to each other to prevent exhaustgas from leaking, both the inner cases are integrated due to rust andthey cannot be easily separated from each other. In contrast, accordingto the first aspect of the invention, it is extremely easy to separateboth the inner cases from each other, and there is a merit that thispoint also enhances maintenance performance and exchanging operabilityof the gas purification bodies.

According to the second aspect of the invention, in the exhaust gaspurification device of the first aspect, the outer side surfaces of theinner cases are provided with bonding flanges protruding radiallyoutward, one ends of the outer cases in the exhaust gas moving directionare fixed to steps formed on the bonding flanges, and the adjoiningbonding flanges are superposed on each other and detachably connected toeach other. Therefore, the outer case can be easily positioned withrespect to the bonding flange due to the existence of the step. When theouter case and the bonding flange are fixed to each other, it ispossible to prevent the outer periphery of the bonding flange frominterfering with a fixing jig such as a welding torch and a welding rod,and the machining operability of the outer case and the bonding flangecan be enhanced.

According to the third aspect of the invention, in the exhaust gaspurification device of the second aspect, the inner case is supported bythe outer case in a state where the inner case is not in direct contactwith the outer case due to existence of the bonding flange. Therefore,mechanical vibration and a deforming force applied to the outer casefrom outside are less prone to be transmitted to the inner case, and itis possible to prevent the inner case itself and the gas purificationbody in the inner case from being damaged, and to prevent the gaspurification body from deviating in position. Further, since the outercase is fitted over the entire outer periphery of the inner case, it ispossible to secure the heat insulation layer (heat insulation region)over the entire outer periphery of the inner case. Hence, it is possibleto reliably prevent a reduction in temperature of exhaust gas in theinner case. It is also possible to prevent a surface temperature of theouter case from rising.

According to the fourth aspect of the invention, in the exhaust gaspurification device of any one of the first to third aspects, an outerside surface of one of the adjoining inner cases is provided with asensor boss body for supporting an exhaust gas sensor, the sensor bossbody projects radially outward from a boss body through hole formed inthe outer case, and a collar which surrounds the sensor boss body andcloses the boss body through hole is fixed to an outer side surface ofthe one inner case. Therefore, the connecting strength between the outercase and the inner case can be enhanced due to the existence of thecollar. Further, it is also possible to easily and reliably preventexhaust gas in the inner case from leaking from the boss body throughhole.

Further, as compared with the conventional structure in which one of theinner case is provided with the diameter-enlarged portion to tightly fitboth the inner cases to each other, distances between the end surfacesof the gas purification bodies and the mounting positions of the exhaustgas sensors can be set to the shortest distances (zero or arbitrarysizes) without being influenced by pipe-spreading margins of the innercases and radius and welding margins of the sensor boss bodies. As aresult, the entire length of the exhaust gas purification device can beshortened, and the exhaust gas purification device can be easilyprovided in various kinds of devices. Since the exhaust gas sensors canbe close enough to the end surfaces of the gas purification bodies tocontact with the end surfaces. Therefore, control performance such asautomatic regeneration of the exhaust gas purification device can beenhanced.

According to the fifth aspect of the invention, in the exhaust gaspurification device of the fourth aspect, a pipe of a differentialpressure sensor as the exhaust gas sensor is connected to the sensorboss body, and the pipe extends along an outer side surface of the outercase. Therefore, the pipe comes close to the outer side surface of theouter case. Hence, when the exhaust gas purification device is assembledinto the engine, the pipe does not hinder so much, and the handlingperformance and mounting performance of the exhaust gas purificationdevice are excellent. Therefore, it is easy to carry out the mountingand assembling operations of the exhaust gas purification device.

According to the sixth aspect of the invention, the exhaust gaspurification device of the first aspect further includes an exhaust gasinlet pipe for exhaust gas from the engine flowing into, and an exhaustgas outlet pipe for exhaust gas passing through the gas purificationbody flowing out, the exhaust gas inlet pipe is mounted on the exhaustgas upstream side outer case such that an exhaust gas introducingpassage is formed by the outer side surface of the exhaust gas upstreamside outer case and the inner side surface of the exhaust gas inletpipe, and at least one of the outer side surface of the exhaust gasupstream side outer case and the inner side surface of the exhaust gasinlet pipe is provided with a rectifier which rectifies a flow ofexhaust gas. Therefore, exhaust gas can be smoothly sent into theexhaust gas purification device due to the existence of the rectifierwithout being largely influenced by the shape of the exhaust gas inletpipe. Therefore, there is an effect that it is possible to flow exhaustgas into the exhaust gas upstream side gas purification body as uniformas possible, and the entire region of the gas purification body can beefficiently utilized.

According to the seventh aspect of the invention, in the exhaust gaspurification device of the sixth aspect, a flange body which connectsboth the outer cases to each other is deviated from a connectionboundary position of both the gas purification bodies. Therefore, it ispossible to secure a length of each of the gas purification bodies inthe exhaust gas moving direction, and to shorten lengths of both theouter cases in the exhaust gas moving direction. Therefore, there is aneffect that rigidity of the outer case is enhanced, a weight thereof isreduced, and the entire length of the exhaust gas purification devicecan be made compact (shortened). There is also a merit that it ispossible to easily prevent exhaust gas from leaking due to the existenceof the flange body for connection.

According to the eighth aspect of the invention, in the exhaust gaspurification device of the sixth or seventh aspect, the rectifier isprovided on each of the outer side surface of the exhaust gas upstreamside outer case and the inner side surface of the exhaust gas inletpipe, the rectifier of the outer case is located on an exhaust gasupstream side, and the rectifier of the exhaust gas inlet pipe islocated on an exhaust gas downstream side. Therefore, although therectifier is located in the introducing passage, there is an effect thatthe outer side surface of the output case and the exhaust gas inlet pipecan be mounted without interfering with each other by simple machiningoperation of the outer side surface of the outer case and the exhaustgas inlet pipe.

According to the ninth aspect of the invention, in the exhaust gaspurification device of any one of the sixth to eighth aspects, anexhaust gas inflow opening which is in communication with the exhaustgas inlet pipe is formed in the exhaust gas upstream side outer case andthe inner case which is incorporated in this outer case, the exhaust gasinflow opening opens in a rectangular shape, and four corners of theexhaust gas inflow opening are formed into arc shapes. Therefore, theexhaust gas inflow opening opens in the rectangular form, and theopening area thereof is increased as wide as possible, therebypreventing an increase in the inflow resistance of exhaust gas. Sincethe four corners are formed into the arc shapes, it is possible toprevent the disturbed flow of exhaust gas passing through the exhaustgas inflow opening. Therefore, there is an effect that variation ininflow pressure of exhaust gas passing through the exhaust gas inflowopening is reduced, and it is possible to flow the exhaust gas into theexhaust gas purification device as uniform as possible.

According to the tenth aspect of the invention, the exhaust gaspurification device of the first aspect further includes an exhaust gasinlet pipe for exhaust gas from the engine flowing into, and an exhaustgas outlet pipe for exhaust gas passing through the gas purificationbody flowing out, a silencer having the exhaust gas outlet pipe ismounted on the exhaust gas downstream side outer case, an exhaust gasintroducing pipe extending in parallel to the exhaust gas movingdirection is incorporated in the silencer, and an exhaust gas upstreamside of the exhaust gas introducing pipe enters the exhaust gasdownstream side inner case. Therefore, it is possible to secure a lengthof the exhaust gas introducing pipe in the exhaust gas moving direction,and to shorten a length of the silencer in the exhaust gas movingdirection. Hence, in the exhaust gas purification device having thesilencer, there is an effect that the entire exhaust gas purificationdevice can be made compact, and the silencing function of the silencercan be maintained and enhanced.

According to the eleventh aspect of the invention, in the exhaust gaspurification device of the tenth aspect, a flange body which connectsboth the outer cases to each other is deviated from a connectionboundary position of both the gas purification bodies, and a flange bodywhich connects the exhaust gas downstream side outer case and thesilencer to each other is deviated from a connection boundary positionof the exhaust gas downstream side gas purification body. Therefore, itis possible to secure a length of each of the gas purification bodies inthe exhaust gas moving direction, and to shorten a length of each of theouter cases in the exhaust gas moving direction. It is also possible toshorten lengths of the exhaust gas downstream side outer case and thesilencer in the exhaust gas moving direction. Hence, there is an effectthat rigidity of the outer case and the silencer is enhanced, a weightthereof is reduced, and the entire length of the exhaust gaspurification device can be made compact (can be shortened). There isalso a merit that it is possible to easily prevent exhaust gas fromleaking due to the existence of the flange body for connection.

According to the twelfth aspect of the invention, in the exhaust gaspurification device of the tenth or eleventh aspect, an exhaust gasupstream side end of the silencer is closed by an inner lid body, theexhaust gas introducing pipe penetrates the inner lid body and entersthe exhaust gas downstream side inner case, and a communication hole fortaking exhaust gas in is formed in a portion of the exhaust gasintroducing pipe located on exhaust gas upstream side of the inner lidbody. Therefore, the communication hole located on exhaust gas upstreamside of the inner lid body contributes to intake of exhaust gas into thesilencer. Hence, there is an effect that a length of the silencer in theexhaust gas moving direction is shortened, a moving distance of exhaustgas itself can be sufficiently secured, and the silencing function ofthe silencer can be further enhanced.

According to the thirteenth aspect of the invention, in the exhaust gaspurification device of any one of the tenth to twelfth aspects, a sensorboss body for supporting an exhaust gas sensor is provided on a portionof an outer peripheral surface of the exhaust gas downstream side innercase which is near a connection boundary position of the gaspurification body such that the sensor boss body penetrates the exhaustgas downstream side outer case, and the sensor boss body is located onan extension of an end surface of the gas purification body whichintersects with the exhaust gas moving direction, and on an extension ofan exhaust gas upstream side end surface of the exhaust gas introducingpipe. Therefore, a disposition distance between the end surface of thegas purification body and the exhaust gas sensor can be set to anextremely short distance (they can be disposed closely). Hence, there isan effect that the entire exhaust gas purification device can be madecompact, the detection precision of the exhaust gas sensor can beenhanced, and regeneration control performance of the exhaust gaspurification device can be enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory sectional view of a DPF in a first embodiment;

FIG. 2 is an external perspective view of the DPF;

FIG. 3 is an external plan view of the DPF;

FIG. 4 is an external bottom view of the DPF;

FIG. 5 is an external front view of the DPF;

FIG. 6 is an external side view of the DPF;

FIG. 7 is a side sectional view of an upstream side of the DPF;

FIG. 8 is a side sectional view of a downstream side of the DPF;

FIG. 9 is an explanatory exploded sectional view of the DPF;

FIG. 10 is a separation side view of grasping flanges (semi-arc bodies);

FIG. 11(a) is an enlarged side sectional view of a catalyst-side bondingflange and FIG. 11(b) is an enlarged side sectional view showing awelding mode;

FIG. 12 is a sectional view showing a mounting portion of a sensor bossbody with respect to a gas temperature sensor;

FIG. 13 is a plan view of a diesel engine provided with the DPF;

FIG. 14 is a sectional view showing a mounting portion of the sensorboss body with respect to a differential pressure sensor;

FIG. 15 is an enlarged sectional view showing the mounting portion ofthe sensor boss body with respect to the gas temperature sensor;

FIG. 16 is an explanatory sectional view of a modification of the DPF ofa structure in which adjoining inner cases are not inserted to eachother;

FIG. 17 is an explanatory sectional view of a modification of the DPF ofa structure in which a heat shield case is omitted;

FIG. 18 is an explanatory sectional view of a DPF in a secondembodiment;

FIG. 19 is an external perspective view of the DPF;

FIG. 20 is an external side view of an exhaust gas upstream side in theDPF;

FIG. 21 is an external side view of an exhaust gas downstream side inthe DPF;

FIG. 22 is an explanatory separation sectional view of the DPF;

FIG. 23 is a separation side view of grasping flanges;

FIG. 24 is an enlarged side sectional view of a catalyst-side bondingflange;

FIG. 25 is an enlarged sectional view showing a mounting portion of asensor boss body located on the exhaust gas upstream side;

FIG. 26 is an enlarged side sectional view of the DPF on the exhaust gasupstream side;

FIG. 27 is an enlarged plan sectional view of the DPF on the exhaust gasupstream side;

FIG. 28 is an enlarged plan sectional view of the DPF on the exhaust gasdownstream side;

FIG. 29 is an enlarged sectional view showing a mounting portion of asensor boss body located on the exhaust gas downstream side;

FIG. 30 is an enlarged side sectional view showing another example of asilencer structure;

FIG. 31 is a side view of a diesel engine provided with a DPF as viewedfrom an exhaust manifold;

FIG. 32 is an external side view showing a mounting structure of theDPF;

FIG. 33 is a side view of the diesel engine provided with a DPF asviewed from a flywheel; and

FIG. 34 is an external side view showing a mounting structure of the DPFon an exhaust gas upstream side.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An exhaust gas purification device in which the present invention of theapplication is embodied will be described below based on the drawings.In the following description, a side of an exhaust gas inflow opening 12of a diesel particulate filter 1 is called left side, and a side of thesilencer 30 is called right side. Such terms indicating the specificdirections and positions are used for convenience sake of description,and they do not limit a technical scope of the invention of theapplication.

1. First Embodiment 1-1. Outline Structure of DPF

An outline structure of an exhaust gas purification device of a firstembodiment will be described first. As shown in FIGS. 1, 6 and 13, acontinuous regeneration type diesel particulate filter 1 (DPF 1,hereinafter) as an exhaust gas purification device is provided. The DPF1 eliminates particulate materials (PM) in exhaust gas discharged from adiesel engine 70, and reduces carbon monoxide (CO) and hydrocarbon (HC)in exhaust gas of the diesel engine 70. The DPF 1 is for collectingparticulate materials (PM) in exhaust gas. The DPF 1 is formed into asubstantially cylindrical shape extending in a lateral direction whichintersects with an output shaft (crankshaft) of the diesel engine 70 asviewed from above. The DPF 1 is disposed on a flywheel housing 78 of thediesel engine 70. An exhaust gas inlet pipe 16 (exhaust gas intake side)and an exhaust gas outlet pipe 34 (exhaust gas discharge side) areprovided on left and right sides of the DPF 1 (one end side and theother end side of a moving direction of exhaust gas), i.e., on left andright sides of the diesel engine 70. The exhaust gas inlet pipe 16 whichis the exhaust gas intake side of the DPF 1 is detachably fastened tothe exhaust manifold 71 of the diesel engine 70 through a bolt. Anexhaust pipe 48 is connected to the exhaust gas outlet pipe 34 which isthe exhaust gas discharge side of the DPF 1.

As shown in FIGS. 1 to 6, a diesel oxidation catalyst 2 such as platinumand a soot filter 3 of a honeycomb structure are arranged serially andaccommodated in a DPF casing 60 made of heatproof metal material throughcylindrical inner cases 4 and 20. The DPF 1 is mounted on the flywheelhousing 78 through a flange-side bracket leg 61 and a casing-sidebracket leg 62 as support bodies. In this case, one end of theflange-side bracket leg 61 is detachably bolt-fastened to an outerperiphery of the DPF casing 60 through a bonding flange 26 (detailsthereof will be described later). One end of the casing-side bracket leg62 is integrally welded and fixed to an outer peripheral surface of theDPF casing 60.

As shown in FIGS. 1 to 6 and 13, the other end of the flange-sidebracket leg 61 is detachably fastened to an upper surface (DPF mountingportion) of the flywheel housing 78 through two finally-fastening bolts88. The other end of the casing-side bracket leg 62 is detachablyfastened to the upper surface (DPF mounting portion) of the flywheelhousing 78 through a temporarily-fastening bolt 87 and thefinally-fastening bolts 88. A notch hole 89 is formed in the other endof the casing-side bracket leg 62. The temporarily-fastening bolt 87 isengaged into the notch hole 89.

That is, when the DPF 1 is assembled into the diesel engine 70, thetemporarily-fastening bolt 87 is first incompletely threadedly fastenedto the upper surface of the flywheel housing 78. Then, an operatorbrings the DPF 1 upward using both hands, the casing-side bracket leg 62is engaged with the temporarily-fastening bolt 87 through the notch hole89, and the DPF 1 is temporarily engaged with the diesel engine 70. Inthis state, the operator can release both hands from the DPF 1.Thereafter, an inlet flange body 17 is fastened to the exhaust manifold71, and the exhaust gas inlet pipe 16 is fixed to the exhaust manifold71.

The flange-side bracket leg 61 and the casing-side bracket leg 62 arefastened to the upper surface of the flywheel housing 78 through thethree finally-fastening bolts 88. The temporarily-fastening bolt 87 isalso completely fastened to detachably fix the DPF 1 to the uppersurface of the flywheel housing 78. The DPF 1 can be detached byreversing the above procedure. As a result, the DPF 1 is stablyconnected to and supported on a rear portion of the diesel engine 70 atthe upper surface of the flywheel housing 78 which is a high rigidmember by the bracket legs 61 and 62 and the exhaust manifold 71. TheDPF 1 can be attached to and detached from the diesel engine 70 by onlyone operator.

In the above configuration, exhaust gas in the diesel engine 70 flowsfrom the exhaust manifold 71 of the diesel engine 70 into the dieseloxidation catalyst 2 in the DPF casing 60, the exhaust gas moves fromthe diesel oxidation catalyst 2 to the soot filter 3 and is purified.Particulate materials in the exhaust gas cannot pass through a porouspartition wall between cells in the soot filter 3. That is, theparticulate materials in the exhaust gas are collected by the sootfilter 3. Thereafter, exhaust gas which passes through the dieseloxidation catalyst 2 and the soot filter 3 is discharged into theexhaust pipe 48.

When the exhaust gas passes through the diesel oxidation catalyst 2 andthe soot filter 3, if a temperature of the exhaust gas exceeds aregeneratable temperature (e.g., about 300° C.), NO (nitric oxide) inthe exhaust gas is oxidized to instable NO₂ (nitrogen dioxide) by theaction of the diesel oxidation catalyst 2. Particulate materialscollected by the soot filter 3 are oxidized and eliminated by O (oxygen)discharged when NO₂ returns to NO. When particulate materials aredeposited on the soot filter 3, since particulate materials are oxidizedand eliminated by holding the temperature of the exhaust gas higher thanthe regeneratable temperature, the collecting ability of particulatematerials of the soot filter 3 restores (soot filter 3 is regenerated).

1-2. Assembling Structure of Diesel Oxidation Catalyst

A structure for assembling the diesel oxidation catalyst 2 as oneexample of an exhaust gas purification body (filter) which purifiesexhaust gas discharged from the diesel engine 70 will be described withreference to FIGS. 1 and 9. The diesel oxidation catalyst 2 is providedin a substantially cylindrical catalyst inner case 4 made of heatproofmetal material. The catalyst inner case 4 is provided in a substantiallycylindrical catalyst outer case 5 made of heatproof metal material. Thatis, the catalyst inner case 4 is fitted over the diesel oxidationcatalyst 2 through a mat-shaped catalyst heat insulator 6 made ofceramic fiber. The diesel oxidation catalyst 2 is protected bypress-fitting the catalyst heat insulator 6 between the diesel oxidationcatalyst 2 and the catalyst inner case 4.

The catalyst outer case 5 is fitted over the catalyst inner case 4through a thin plate support body 7 having an L-shaped cross section.The catalyst outer case 5 is one of elements constituting the DPF casing60. The diesel oxidation catalyst 2 is protected by the catalyst heatinsulator 6. Stresses (mechanical vibration and deforming force) of thecatalyst outer case 5 transmitted to the catalyst inner case 4 arereduced by the thin plate support body 7.

As shown in FIGS. 1 and 9, a disk-like side lid body 8 is fixed to oneends of the catalyst inner case 4 and the catalyst outer case 5 bywelding. An outer lid body 9 is fastened to an outer surface of the sidelid body 8 through a bolt and a nut. The side lid body 8 and a gasinflow-side end surface 2 a of the diesel oxidation catalyst 2 areseparated from each other by a given distance L1 (gas inflow space 11).The exhaust gas inflow space 11 is formed between the side lid body 8and the gas inflow-side end surface 2 a of the diesel oxidation catalyst2. The exhaust gas inflow opening 12 facing the exhaust gas inflow space11 opens on the catalyst inner case 4 and the catalyst outer case 5. Aclosing ring body 15 is sandwiched and fixed between an opening edge ofthe catalyst inner case 4 and an opening edge of the catalyst outer case5. Since a gap between the opening edge of the catalyst inner case 4 andthe opening edge of the catalyst outer case 5 is closed by the closingring body 15, it is possible to prevent exhaust gas from flowing inbetween the catalyst inner case 4 and the catalyst outer case 5.

As shown in FIGS. 1 to 6, and 9, the exhaust gas inlet pipe 16 isdisposed on an outer peripheral surface of the catalyst outer case 5 inwhich the exhaust gas inflow opening 12 is formed. The inlet flange body17 is welded and fixed to one of opening ends of an exhaust gas inletpipe 16. The inlet flange body 17 is detachably fastened to the exhaustmanifold 71 of the diesel engine 70 through a bolt. One of opening endsof the exhaust gas inlet pipe 16 is brought into communication with theexhaust manifold 71. The other opening end of the exhaust gas inlet pipe16 is welded to an outer peripheral surface of the catalyst outer case 5to cover the exhaust gas inflow opening 12 from outside. A pair ofreinforcing bracket bodies 18 is welded and fixed between the outerperipheral surface of the catalyst outer case 5 and a side edge of theinlet flange body 17. Connection strength of each of the exhaustmanifold 71 and the exhaust gas inlet pipe 16 is secured due to theexistence of both the reinforcing bracket bodies 18.

According to this configuration, exhaust gas in the diesel engine 70flows from the exhaust manifold 71 into the exhaust gas inlet pipe 16,and flows from the exhaust gas inlet pipe 16 and enters the exhaust gasinflow space 11 through the exhaust gas inflow opening 12. Exhaust gaswhich reaches the exhaust gas inflow space 11 is supplied from the leftgas inflow-side end surface 2 a into the diesel oxidation catalyst 2.Nitrogen dioxide (NO₂) is generated by the oxidization action of thediesel oxidation catalyst 2.

1-3. Assembling Structure of Soot Filter

A structure for assembling the soot filter 3 as one example of theexhaust gas purification body (filter) which purifies exhaust gasdischarged from the diesel engine 70 will be described with reference toFIGS. 1 and 9. The soot filter 3 is provided in a substantiallycylindrical filter inner case 20 made of heatproof metal material. Thefilter inner case 20 is provided in a substantially cylindrical filterouter case 21 made of heatproof metal material. That is, the filterinner case 20 is fitted over the soot filter 3 through a mat-shapedfilter heat insulator 22 made of ceramic fiber. The filter outer case 21is one of elements constituting the DPF casing 60 together with thecatalyst outer case 5. The soot filter 3 is protected by press-fittingthe filter heat insulator 22 between the soot filter 3 and the filterinner case 20.

As shown in FIGS. 1 and 9, the catalyst inner case 4 is formed into acylindrical shape having a straight ridge line and includes an upstreamside cylindrical portion 4 a in which the diesel oxidation catalyst 2 isaccommodated and a downstream side cylindrical portion 4 b into whichthe later-described filter inner case 20 is inserted. The upstream sidecylindrical portion 4 a and the downstream side cylindrical portion 4 bare cylinders having substantially the same diameters and are integrallyformed. The catalyst inner case 4 and the filter inner case 20 areformed into cylindrical shapes having substantially the same diameters.That is, the catalyst inner case 4 and the filter inner case 20 arecylindrical in shape having straight ridge lines, and diameters of bothends thereof are equal to each other.

An outer peripheral surface of the downstream side cylindrical portion 4b in the catalyst inner case 4 is provided with a heat shield case 190extending toward an exhaust gas downstream side. The heat shield case190 is one of elements constituting the catalyst inner case 4. The heatshield case 190 is formed into a cylindrical shape, and a diameter of anupstream side of the heat shield case 190 is smaller than that of thedownstream side of the heat shield case 190. An upstream side end 190 aof the heat shield case 190 is fitted over, welded and fixed to theouter peripheral surface of the downstream side cylindrical portion 4 bin the catalyst inner case 4. In this case, the upstream side end 190 aof the heat shield case 190 is located in exhaust gas upstream side ofan exhaust gas downstream side end surface (opening end surfacecorresponding to gas outflow end surface 2 b of diesel oxidationcatalyst 2) of the catalyst inner case 4. Hence, an upstream side gap 23a is formed between the outer peripheral surface of the downstream sidecylindrical portion 4 b in the catalyst inner case 4 and an inner sidesurface of the heat shield case 190.

An outer diameter of the diesel oxidation catalyst 2 and an outerdiameter of the soot filter 3 are equal to each other. A thickness ofthe catalyst heat insulator 6 and a thickness of the filter heatinsulator 22 are also about the same. The catalyst inner case 4 and thefilter inner case 20 are formed from material having the same thickness.Exhaust gas upstream side (exhaust gas intake side) of the filter innercase 20 is inserted into the heat shield case 190. That is, theadjoining catalyst inner case 4 and the filter inner case 20 are of adouble-layer structure in which the filter inner case 20 is insertedinto the catalyst inner case 4. As the double-layer structure, thecatalyst inner case 4 may be inserted into the filter inner case 20. Inthis case, the heat shield case 190 is provided on the side of thefilter inner case 20 such that the heat shield case 190 extends towardthe exhaust gas upstream side.

In this embodiment, an outer diameter of the filter inner case issmaller than an inner diameter of the exhaust gas downstream side of theheat shield case 190. Hence, in a state where the exhaust gas upstreamside of the filter inner case 20 is inserted into the heat shield case190, a downstream side gap 23 as a loosely-fitting gap is formed betweenthe filter inner case 20 and an inner side surface of the heat shieldcase 190. A gap distance of the downstream side gap 23 is set to a size(e.g., 2 mm) which is greater than thicknesses of the inner cases 4 and20 (e.g., 1.5 mm). For example, even if the inner cases 4 and 20 becomerusty or deform, the exhaust gas upstream side of the filter inner case20 can be easily put into or pulled out from the heat shield case 190.

The exhaust gas purification device includes a thin ring-likecatalyst-side bonding flange 25 which is welded and fixed to an outerperiphery of the catalyst inner case 4 (in this embodiment, heat shieldcase 190), and a thin ring-like filter-side bonding flange 26 which iswelded and fixed to an outer periphery of the filter inner case 20. Thecatalyst-side bonding flange 25 and the filter-side bonding flange 26are formed into doughnut shapes having substantially L-shaped crosssections. An inner periphery of the catalyst-side bonding flange 25 iswelded and fixed to the exhaust gas downstream side of the outerperiphery of the heat shield case 190. An outer periphery of thecatalyst-side bonding flange 25 projects (protrudes) toward an outerperiphery (radial direction, radially outward direction) of thecatalyst-side bonding flange 25. A step-wise step 25 a is formed on abent angle portion of the catalyst-side bonding flange 25. An exhaustgas downstream side end of the catalyst outer case 5 is welded and fixedto the step 25 a. An inner periphery of the filter-side bonding flange26 is welded and fixed to a longitudinally halfway portion (halfwayportion in exhaust gas moving direction) of the outer periphery of thefilter inner case 20. An outer periphery of the filter-side bondingflange 26 projects (protrudes) toward the outer periphery (radialdirection, radially outward direction) of the filter outer case 21. Astep-wise step 26 a is formed on a bent angle portion of the filter-sidebonding flange 26. An exhaust gas upstream side end of the filter outercase 21 is welded and fixed to the step 26 a.

As shown in FIGS. 1 to 5, 9 and 12, the catalyst-side bonding flange 25and the filter-side bonding flange 26 are butted against each otherthrough a gasket 24. The bonding flanges 25 and 26 are sandwiched fromboth sides in the exhaust gas moving direction by a pair of thickcentral grasping flanges 51 and 52 which surround outer peripheries ofthe outer cases 5 and 21. The central grasping flanges 51 and 52 arefastened to each other through bolt 27 and nut 28 to sandwich thebonding flanges 25 and 26. According to this configuration, the catalystouter case 5 and the filter outer case 21 are detachably connected toeach other.

As shown in FIGS. 1 and 12, in a state where the exhaust gas upstreamside end of the filter outer case 21 is connected to the exhaust gasdownstream side end of the catalyst outer case 5 through the centralgrasping flanges 51 and 52 and the bonding flanges 25 and 26, a catalystdownstream side space 29 is formed between the diesel oxidation catalyst2 and the soot filter 3. That is, a gas outflow end surface 2 b of thediesel oxidation catalyst 2 (catalyst inner case 4) and an intake sideend surface 3 a of the soot filter 3 (filter inner case 20) are opposedto each other at a sensor mounting distance L2 from each other.

As shown in FIGS. 1 and 9, a cylinder length L4 of the catalyst outercase 5 in the exhaust gas moving direction is longer than a cylinderlength L3 of the upstream side cylindrical portion 4 a of the catalystinner case 4 in the exhaust gas moving direction. A cylinder length L6of the filter outer case 21 in the exhaust gas moving direction isshorter than a cylinder length L5 of the filter inner case 20 in theexhaust gas moving direction. A total length (L2+L3+L5) of the sensormounting distance L2 of the catalyst downstream side space 29, thecylinder length L3 of the upstream side cylindrical portion 4 a in thecatalyst inner case 4, and the cylinder length L5 of the filter innercase 20 is substantially equal to a total length (L4+L6) of the cylinderlength L4 of the catalyst outer case 5 and the cylinder length L6 of thefilter outer case 21.

The exhaust gas upstream side end of the filter inner case 20 projectsfrom the exhaust gas upstream side end of the filter outer case 21 by alength difference (L7≈L5−L6) between the cases 20 and 21. Hence, in astate where the filter outer case 21 is connected to the catalyst outercase 5, the exhaust gas upstream side end of the filter inner case 20 isinserted into the exhaust gas downstream side of the catalyst outer case5 (downstream side cylindrical portion 4 b of the catalyst inner case 4)by the upstream side size L7 of the filter inner case 20 projecting fromthe filter outer case 21. That is, the exhaust gas upstream side of thefilter inner case 20 is inserted into the downstream side cylindricalportion 4 b (catalyst downstream side space 29) such that the exhaustgas upstream side of the filter inner case 20 can be pulled out.

In the above-described configuration, nitrogen dioxide (NO₂) generatedby the oxidization action of the diesel oxidation catalyst 2 is suppliedfrom the intake side end surface 3 a into the soot filter 3. Particulatematerials (PM) included in exhaust gas of the diesel engine 70 arecollected by the soot filter 3, and the particulate materials arecontinuously oxidized and eliminated by the nitrogen dioxide (NO₂). Inaddition to elimination of particulate materials (PM) in exhaust gas ofthe diesel engine 70, contents of carbon monoxide (CO) and hydrocarbon(HC) in exhaust gas of the diesel engine 70 are reduced.

1-4. Assembling Structure of Silencer

Next, a structure of the silencer 30 which attenuates sound of exhaustgas discharged from the diesel engine 70 will be described withreference to FIGS. 1, 8 and 9. As shown in FIGS. 1, 8 and 9, thesilencer 30 includes a substantially cylindrical silencing inner case 31made of heatproof metal material, a substantially cylindrical silencingouter case 32 made of heatproof metal material, and a disk-like side lidbody 33 fixed to a downstream side end of the silencing outer case 32 bywelding. The silencing inner case 31 is provided in the silencing outercase 32. The silencing outer case 32 forms the DPF casing 60 togetherwith the catalyst outer case 5 and the filter outer case 21. A diameterof the cylindrical silencing outer case 32 is substantially equal tothose of the cylindrical catalyst outer case 5 and the cylindricalfilter outer case 21.

Disk-like inner lid bodies 36 and 37 are fixed to both ends of thesilencing inner case 31 in the exhaust gas moving direction by welding.A pair of exhaust gas introducing pipes 38 is provided between the innerlid bodies 36 and 37. The exhaust gas upstream side end of each of theexhaust gas introducing pipes 38 penetrates the upstream inner lid body36. The exhaust gas downstream side end of each of the exhaust gasintroducing pipes 38 is closed by the downstream inner lid body 37. Aplurality of communication holes 39 are formed in a halfway portion ofeach of the exhaust gas introducing pipes 38. The expansion chamber 45is in communication with each of the exhaust gas introducing pipes 38through the communication holes 39. The expansion chamber 45 is formedin the silencing inner case 31 (between inner lid bodies 36 and 37).

The exhaust gas outlet pipe 34 disposed between the exhaust gasintroducing pipes 38 penetrates the silencing inner case 31 and thesilencing outer case 32. One end of the exhaust gas outlet pipe 34 isclosed by an outlet lid body 35. A large number of exhaust gas holes 46are formed in the entire exhaust gas outlet pipe 34 in the silencinginner case 31. Each of the exhaust gas introducing pipes 38 is incommunication with the exhaust gas outlet pipe 34 through the pluralityof communication holes 39, the expansion chamber 45, and the largenumber of exhaust gas holes 46. The exhaust pipe 48 is connected to theother end of the exhaust gas outlet pipe 34. In the above-describedconfiguration, exhaust gas which enters each of the exhaust gasintroducing pipes 38 of the silencing inner case 31 passes through theexhaust gas outlet pipe 34 through the plurality of communication holes39, the expansion chamber 45, and the large number of exhaust gas holes46, and the exhaust gas is discharged from the silencer 30 through theexhaust pipe 48.

As shown in FIGS. 1 and 9, an inner diameter side of a thin ring-likefilter outlet-side bonding flange 40 is welded and fixed to the exhaustgas downstream side end of the filter inner case 20. An outer diameterside of the filter outlet-side bonding flange 40 protrudes toward anouter periphery (radial direction, radially outward direction) of thefilter outer case 21. A step-wise step 40 a is formed on a bent angleportion of the filter outlet-side bonding flange 40. An exhaust gasdownstream side end of the filter outer case 21 is welded and fixed tothe step 40 a of the filter outlet-side bonding flange 40. A thinsilencing-side bonding flange 41 protruding toward an outer periphery(radially outward) of the silencing outer case 32 is welded and fixed tothe exhaust gas upstream side end of the silencing inner case 31. Theexhaust gas upstream side of the silencing inner case 31 projects, by apredetermined cylinder size L10, toward a location closer to the exhaustgas upstream side than the silencing-side bonding flange 41. The exhaustgas upstream side end of the silencing outer case 32 is welded and fixedto a portion of an outer peripheral surface of the silencing inner case31 which is closer to the exhaust gas downstream side than thesilencing-side bonding flange 41.

As shown in FIGS. 1 and 7 to 10, the filter outlet-side bonding flange40 and the silencing-side bonding flange 41 are abutted against eachother through the gasket 24, and the bonding flanges 40 and 41 aresandwiched from both sides in the exhaust gas moving direction by a pairof thick outlet grasping flanges 53 and 54 which surround outerperipheries of the outer cases 21 and 32. The outlet grasping flanges 53and 54 are fastened to each other through bolts 42 and nuts 43 tosandwich the bonding flanges 40 and 41. According to this operation, thefilter outer case 21 and the silencing outer case 32 are detachablyconnected to each other.

As shown in FIGS. 1 and 9, a cylinder length L9 of the silencing outercase 32 in the exhaust gas moving direction is shorter than a cylinderlength L8 of the silencing inner case 31 in the exhaust gas movingdirection. The exhaust gas upstream side end of the silencing inner case31 projects from the exhaust gas upstream side end (bonding flange 41)of the silencing outer case 32 by a length difference (L10≈L8−L9)between the cases 31 and 32. That is, in a state where the silencingouter case 32 is connected to the filter outer case 21, the exhaust gasupstream side end of the silencing inner case 31 is inserted into thefilter downstream side space 49 formed in the exhaust gas downstreamside end (filter outlet-side bonding flange 40) of the filter outer case21 by the size L10 by which the upstream side end of the silencing innercase 31 projects.

1-5. Connecting Structure of Adjoining Outer Cases

Next, a structure for connecting adjoining outer cases 5, 21 and 32 toone another will be described with reference to FIGS. 1 and 7 to 10. Asshown in FIGS. 1 and 7 to 10, a thick central grasping flange 51 (52)includes semi-arc bodies 51 a and 51 b (52 a, 52 b) divided into aplurality of bodies (two, in the embodiment) in a circumferentialdirection of the catalyst outer case 5 (filter outer case 21). Each ofthe semi-arc bodies 51 a and 51 b (52 a, 52 b) is formed into an are(substantially semi-circular horseshoe shape). In a state where thefilter outer case 21 is connected to the catalyst outer case 5, ends ofthe semi-arc bodies 51 a and 51 b (52 a, 52 b) are butted against(connected to) each other along the circumferential direction. That is,the outer periphery of the catalyst outer case 5 (filter outer case 21)is annularly surrounded by the semi-arc bodies 51 a and 51 b (52 a, 52b).

The central grasping flange 51 (52) is provided with a plurality of boltfastening portions 55 having through holes. The bolt fastening portions55 are provided at equal distances from one another in thecircumferential direction. In this embodiment, eight bolt fasteningportions 55 are provided per one set of central grasping flanges 51.Each of the semi-arc bodies 51 a and 51 b (52 a, 52 b) is provided withfour bolt fastening portions 55 at equal distances from one another inthe circumferential direction. Bolt holes 56 corresponding to the boltfastening portions 55 of the central grasping flange 51 (52) are formedin the catalyst-side bonding flange 25 and the filter-side bondingflange 26 to penetrate these flanges 25 and 26.

When the catalyst outer case 5 and the filter outer case 21 areconnected to each other, the outer periphery of the catalyst outer case5 is surrounded by both the catalyst-side semi-arc bodies 51 a and 51 b,the outer periphery of the filter outer case 21 is surrounded by thefilter-side semi-arc bodies 52 a and 52 b, and the catalyst-side bondingflange 25 and the filter-side bonding flange 26 which sandwich thegasket 24 are sandwiched from both sides in the exhaust gas movingdirection by the semi-arc bodies 51 a, 51 b, 52 a, and 52 b (centralgrasping flanges 51 and 52). Next, bolts 27 are inserted into the boltfastening portions 55 of the both side central grasping flanges 51 and52 and the bolt holes 56 of both the bonding flanges 25 and 26, andtightened into nuts 28. As a result, both the bonding flanges 25 and 26are sandwiched between and fixed by both the central grasping flanges 51and 52, and the connecting operation of the catalyst outer case 5 andthe filter outer case 21 is completed. Here, the butted portions of theends of the catalyst-side semi-arc bodies 51 a and 51 b and thefilter-side semi-arc bodies 52 a and 52 b are located such that theirphases are deviated from each other by 72°.

As shown in FIGS. 1 and 7 to 10, the thick outlet grasping flange 53(54) includes semi-arc bodies 53 a and 53 b (54 a, 54 b) divided into aplurality of bodies (two, in this embodiment) in the circumferentialdirection of the filter outer case 21 (silencing outer case 32). Each ofthe semi-arc bodies 53 a and 53 b (54 a, 54 b) in this embodiment arebasically the same as the semi-arc bodies 51 a and 51 b (52 a, 52 b) ofthe central grasping flange 51 (52). The outlet grasping flange 53 (54)are also provided with a plurality of bolt fastening portions 57 havingthrough holes at equal distances from one another in the circumferentialdirection. Bolt holes 58 corresponding to the bolt fastening portions 57of the outlet grasping flange 53 (54) are formed in the filteroutlet-side bonding flange 40 and the silencing-side bonding flange 41to penetrate these flanges 40 and 41.

When the filter outer case 21 and the silencing outer case 32 areconnected to each other, the outer periphery of the filter outer case 21is surrounded by both the filter outlet-side semi-arc bodies 53 a and 53b, the outer periphery of the silencing outer case 32 is surrounded byboth the silencing-side semi-arc bodies 54 a and 54 b, and the filteroutlet-side bonding flange 40 and the silencing-side bonding flange 41which sandwich the gasket 24 are sandwiched from both sides in theexhaust gas moving direction by the semi-arc bodies 53 a, 53 b, 54 a,and 54 b (outlet grasping flange 53, 54). Next, bolts 42 are insertedinto the bolt fastening portions 57 of both side outlet grasping flanges53 and 54 and the bolt holes 58 of both the bonding flanges 40 and 41,and tightened into nuts 43. As a result, both the bonding flanges 40 and41 are sandwiched between and fixed by both the outlet grasping flanges53 and 54, and the connecting operation of the filter outer case 21 andthe silencing outer case 32 is completed. Here, the butted portions ofthe ends of the filter outlet-side semi-arc bodies 53 a and 53 b and thesilencing-side semi-arc bodies 54 a and 54 b are located such that theirphases are deviated from each other by 72°.

As shown in FIGS. 1 and 7 to 10, the flange-side bracket leg 61 as thesupport body which makes the DPF casing 60 (outer cases 5, 21, 32) besupported by the diesel engine 70 is mounted on at least one of thegrasping flanges 51 to 54. In this embodiment, support body fasteningportions 59 having through holes are integrally formed on the onesemi-arc body 53 a of the filter outlet-side outlet grasping flange 53at two locations between adjoining bolt fastening portions 57. Mountingbosses 86 corresponding to the support body fastening portions 59 areintegrally formed on the flange-side bracket leg 61.

In the above-described configuration, by fastening the mounting bosses86 of the flange-side bracket leg 61 to the support body fasteningportions 59 of the one filter outlet-side semi-arc body 53 a, theflange-side bracket leg 61 is detachably fixed to the filter outlet-sideoutlet grasping flange 53. One end of the casing-side bracket leg 62 iswelded and fixed to the outer periphery of the DPF casing 60 (catalystouter case 5), the other ends of the bracket legs 61 and 62 are fastenedto the upper surface of the flywheel housing 78 (DPF mounting portion)through bolts as described above.

As shown in FIGS. 1 and 7 to 10, the exhaust gas purification deviceincludes two gas purification bodies 2 and 3 (diesel oxidation catalyst2 and soot filter 3) which purify exhaust gas discharged from the engine70, the inner cases 4, 20, and 31 in which the gas purification bodies 2and 3 are incorporated, and the outer cases 5, 21, and 32 in which theinner cases 4, 20, and 31 are incorporated. The inner cases 4, 20, and31 are connected to the outer cases 5, 21, and 32 through the bondingflanges 25, 26, 40, and 41 which protrude toward outer peripheries ofthe outer cases 5, 21, and 32. The exhaust gas purification deviceincludes a plurality of sets of combination of the gas purificationbodies 2 and 3, the inner cases 4, 20, and 31 and the outer cases 5, 21,and 32. The bonding flanges 25 and 26 (40, 41) are sandwiched betweenand fixed by the pair of grasping flanges 51 and 52 (53, 54), therebyconnecting the plurality of outer cases 5, 21, and 32 to each other.

According to this configuration, the adjoining bonding flanges 25 and 26(40, 41) can be sandwiched from both sides by the grasping flanges 51and 52 (53, 54) and can be (tightly) connected to each other underpressure. Further, the grasping flanges 51 to 54 are not welded to theouter cases 5, 21, and 32 and are formed separately from them. In arelation between the grasping flanges 51 to 54 and the outer cases 5, 21and 32, there is no fear that stress concentration and distortion causedby welding are generated. Hence, substantially uniformpressure-connecting force can be applied to the entire bonding flanges25 and 26 (40, 41), and a surface pressure of sealing surfaces(sandwiching surfaces) of the grasping flanges 51 to 54 can bemaintained in a high state. As a result, it is possible to reliablyprevent exhaust gas from leaking between the bonding flanges 25 and 26(40, 41).

As shown in FIGS. 1 and 7 to 10, each of the grasping flanges 51 to 54includes horseshoe-shaped semi-arc bodies 51 a and 51 b (52 a, 52 b, 53a, 53 b, 54 a, 54 b) divided into a plurality of bodies in thecircumferential direction of the outer cases 5, 21, and 32, and theplurality of semi-arc bodies 51 a and 51 b (52 a, 52 b, 53 a, 53 b, 54a, 54 b) surround the outer peripheries of the outer cases 5, 21, and32. Therefore, although the grasping flange 51 to 54 include theplurality of semi-arc bodies 51 a and 51 b (52 a, 52 b, 53 a, 53 b, 54a, 54 b), they can be assembled as in one body. Hence, it is easy toassemble the grasping flanges 51 to 54 as compared with ring-likeflanges, and the assembling operability can be enhanced. The DPF 1having excellent sealing performance can be formed while suppressing amachining cost and an assembling cost.

1-6. Detailed of Structure of Bonding Flange

Next, detailed structures of the bonding flanges 25, 26, and 40 will bedescribed with reference to FIGS. 11(a) and (b). Since the bondingflanges 25, 26, and 40 basically have the same structures, thecatalyst-side bonding flange 25 which is welded and fixed to thecatalyst inner case 4 and the catalyst outer case 5 will be described asa representative example. As shown in FIGS. 11(a) and (b), the step-wisestep 25 a is formed on the bent angle portion of the catalyst-sidebonding flange 25. The exhaust gas downstream side end of the catalystouter case 5 is fitted over the step 25 a, and the step 25 a is weldedand fixed to the exhaust gas downstream side end of the catalyst outercase 5.

In this case, since the exhaust gas downstream side end of the catalystouter case 5 is butted against the step 25 a of the catalyst-sidebonding flange 25, it is possible to easily position the catalyst outercase 5 with respect to the catalyst-side bonding flange 25 due to theexistence of the step 25 a. The welding between the catalyst outer case5 and the step 25 a is not superposing fillet welding but is a buttwelding. A welding torch 192 and a welding rod 193 (see FIG. 11(b)) aretilted so that they are separated from the outer periphery of thecatalyst-side bonding flange 25 or they are made to stand up vertically,and they can be brought close to the butted portion between the catalystouter case 5 and the step 25 a, and welded to each other. Therefore,when the catalyst outer case 5 and the catalyst-side bonding flange 25are welded to each other, it is possible to prevent the outer peripheryof the catalyst-side bonding flange 25 from interfering with the weldingtorch 192 and the welding rod 193, and the welding operability(machining operability) between the catalyst outer case 5 and thecatalyst-side bonding flange 25 can be enhanced. Even if the length ofthe catalyst-side bonding flange 25 in the exhaust gas moving directionis short, it is possible to weld the catalyst outer case 5 and thecatalyst-side bonding flange 25 to each other due to the existence ofthe step 25 a. Therefore, a region of the catalyst-side bonding flange25 which comes into direct contact with outside air can be reduced.Hence, it is possible to prevent reduction in temperature of exhaust gasin the catalyst inner case 4 and the filter inner case 20.

An L-shaped inner diameter-side end 25 b in the catalyst-side bondingflange 25 extends along the exhaust gas moving direction of the catalystinner case 4 (catalyst outer case 5). In this case, the innerdiameter-side end 25 b extends toward the exhaust gas upstream side. Theinner diameter-side end 25 b is fitted over the exhaust gas downstreamside end of the catalyst inner case 4, and the inner diameter-side end25 b is welded and fixed to the outer peripheral surface of the catalystinner case 4 (fillet welding). An L-shaped outer diameter-side end 25 c(outer peripheral side) in the catalyst-side bonding flange 25 extendsin the radial direction (radially outward direction) from the outerperiphery of the catalyst outer case 5. High rigidity of thecatalyst-side bonding flange 25 is secured by a step-wise crosssectional shape of the catalyst-side bonding flange 25.

As can be found from the above description and FIGS. 1 and 9, since thecatalyst-side bonding flange 25 is interposed between the catalyst innercase 4 and the catalyst outer case 5, the catalyst inner case 4 issupported in a state where it is not in direct contact with the catalystouter case 5. Hence, mechanical vibration and a deforming forceexternally applied to the catalyst outer case 5 are less prone to betransmitted to the catalyst inner case 4, and it is possible to preventthe catalyst inner case 4 itself and the diesel oxidation catalyst 2therein from being damaged, and to prevent the diesel oxidation catalyst2 from deviating in position. Since the catalyst outer case 5 is fittedover the entire region of the catalyst inner case 4, it is possible tosecure a heat barrier (heat insulation region) over the entire outerperiphery of the catalyst inner case 4. Hence, it is possible toreliably prevent the reduction in exhaust gas temperature in thecatalyst inner case 4. It is also possible to prevent the increase inthe surface temperature of the catalyst outer case 5.

The nuts 28 are threadedly engaged with the bolts 27 which pass throughthe bolt holes 56 in the grasping flanges 51 and 52 and the bondingflanges 25 and 26, thereby fastening the grasping flanges 51 and 52 andthe bonding flanges 25 and 26 to each other, and the outer diameter-sideend 25 c of the catalyst-side bonding flange 25 is sandwiched betweenthe grasping flanges 51 and 52 as described above.

1-7. Mounting Structure of Gas Temperature Sensor

Next, an upstream side gas temperature sensor 109 (downstream side gastemperature sensor 112) provided in the DPF 1 will be described withreference to FIGS. 1, 12, and 15. A sensor boss body 110 for supportingthe gas temperature sensor 109 (112) which is one example of an exhaustgas sensor is provided on an outer peripheral surface of one of theadjoining inner cases 4 and 20 which is located radially outward. Inthis embodiment, one end of the cylindrical sensor boss body 110 iswelded and fixed to a portion of the outer peripheral surface of thecatalyst inner case 4 (more specifically, heat shield case 190)corresponding to the catalyst downstream side space 29. The other end ofthe sensor boss body 110 extends in the radial direction (radiallyoutward direction) toward an outer side of the catalyst outer case 5from the boss body through hole 5 a formed in the catalyst outer case 5.A sensor mounting bolt 111 is threadedly engaged with the other end ofthe sensor boss body 110. The thermistor-shaped upstream side gastemperature sensor 109 penetrates the sensor mounting bolt 111, and theupstream side gas temperature sensor 109 is supported by the sensor bossbody 110 through the sensor mounting bolt 111. A detecting portion ofthe upstream side gas temperature sensor 109 projects into the catalystdownstream side space 29.

As shown in FIGS. 12 and 15, a collar 194 which surrounds the sensorboss body 110 is fixed to the outer peripheral surface of the catalystinner case 4 (more specifically, heat shield case 190). A tip endsurface of the collar 194 is in intimate contact with an innerperipheral surface of the catalyst outer case 5, and the tip end surfacecloses, from inside, the boss body through hole 5 a. The sensor bossbody 110 penetrates the boss body through hole 5 a. Hence, a connectionstrength (rigidity) between the catalyst outer case 5 and the catalystinner case 4 (more specifically, heat shield case 190) can be enhanceddue to existence of the collar 194. It is possible to easily andreliably prevent exhaust gas in the catalyst inner case 4 and the filterinner case 20 from leaking from the boss body through hole 5 a.

According to this configuration, when exhaust gas is discharged from thegas outflow end surface 2 b of the diesel oxidation catalyst 2, atemperature of the exhaust gas is detected by the upstream side gastemperature sensor 109. In this case, a position of the sensor boss body110 can be located upstream of the gas outflow end surface 2 b of thediesel oxidation catalyst 2. Therefore, the sensor boss body 110 can bedisposed on the outer peripheral surface of the catalyst inner case 4(heat shield case 190) such that the upstream side gas temperaturesensor 109 approaches the gas outflow end surface 2 b until the upstreamside gas temperature sensor 109 comes into contact with the gas outflowend surface 2 b of the diesel oxidation catalyst 2. The inner cases 4and 20 can be thinned by thickening the outer cases 5 and 21,temperatures of the diesel oxidation catalyst 2 and the soot filter 3can be maintained higher than the regeneratable temperature and the DPF1 can be reduced in weight. As shown in FIG. 1, the thermistor-shapeddownstream side gas temperature sensor 112 is mounted on the sensor bossbody 110 through the sensor mounting bolt 111, and the downstream sidegas temperature sensor 112 detects a temperature of exhaust gas of adischarge side end surface 3 b of the soot filter 3. The sensor bossbody 110 in this case penetrates a boss body through hole 21 a of thefilter outer case 21.

1-8. Mounting Structure of Differential Pressure Sensor

Next, a differential pressure sensor 63 provided in the DPF 1 will bedescribed with reference to FIGS. 13 and 14. The differential pressuresensor 63 which is one example of an exhaust gas sensor sandwiches thesoot filter 3 in the DPF 1 and detects a pressure difference of exhaustgas between upstream side and downstream side. A deposited amount ofparticulate materials of the soot filter 3 is converted based on thepressure difference so that a clogged state of the DPF 1 can be grasped.That is, acceleration control means or intake throttle control means(both not shown) is operated based on the pressure difference of exhaustgas detected by the differential pressure sensor 63 so that theregeneration of the soot filter 3 can be automatically controlled.

A sensor bracket 66 is fastened to a silencing-side outlet graspingflange 54 through a bolt, and the sensor bracket 66 is disposed on anupper surface of the DPF casing 60. A detecting body 67 of thedifferential pressure sensor 63 is mounted on the sensor bracket 66. Anupstream side pipe joint body 64 and a downstream side pipe joint body65 are connected to a detecting body 67 of the differential pressuresensor 63 through an upstream side sensor pipe 68 and a downstream sidesensor pipe 69 respectively. Like the sensor boss body 110, a sensorboss body 113 is disposed on the DPF casing 60. The upstream side pipejoint body 64 (downstream side pipe joint body 65) is fastened to thesensor boss body 113 through pipe joint bolts 114.

As described above, an upstream side gap 23 a is formed between an outerperipheral surface of the downstream side cylindrical portion 4 b in thecatalyst inner case 4 and an inner peripheral surface of the heat shieldcase 190. One end of the cylindrical sensor boss body 113 is welded andfixed to an exhaust gas upstream side outer peripheral surface of theheat shield case 190. The other end of the sensor boss body 113 extendsin the radial direction (radially outward direction) toward an outerside of the catalyst outer case 5 from the boss body through hole 5 aformed in the catalyst outer case 5, and the upstream side pipe jointbody 64 is fastened to the sensor boss body 113 through the pipe jointbolts 114. The detecting body 67 of the differential pressure sensor 63is connected to the upstream side pipe joint body 64 through theupstream side sensor pipe 68. The collar 194 surrounding the sensor bossbody 113 is also fixed to the sensor boss body 113, and the collar 194closes a boss body through hole 5 a from inside.

In this case, as can be seen in FIGS. 13 and 14, one end of the upstreamside sensor pipe 68 is connected to the upstream side pipe joint body 64fastened to the sensor boss body 113 from a direction intersecting witha projecting direction of the sensor boss body 113. The upstream sidesensor pipe 68 itself extends along the outer peripheral surface of thecatalyst outer case 5, and the other end of the upstream side sensorpipe 68 is connected to the detecting body 67 mounted on the sensorbracket 66. According to this configuration, since the upstream sidesensor pipe 68 is close to the DPF casing 60, when the DPF 1 isassembled into the diesel engine 70 for example, the upstream sidesensor pipe 68 does not hinder so much, and the mounting operability andthe assembling operability of the DPF 1 are excellent. Therefore, it iseasy to mount and assemble the DPF 1.

As shown in FIG. 14, a sensor opening 190 b is formed in the upstreamside gap 23 a. A hollow portion in the sensor boss body 113 is incommunication with the upstream side gap 23 a through the sensor opening190 b. Exhaust gas is discharged from the gas outflow end surface 2 b ofthe diesel oxidation catalyst 2 into the catalyst downstream side space29. According to this, a portion of the exhaust gas in the catalystdownstream side space 29 moves toward the detecting body 67 through theupstream side gap 23 a, the sensor opening 190 b, the hollow portion ofthe sensor boss body 113, the hollow portion of the upstream side pipejoint body 64 and the upstream side sensor pipe 68.

According to this configuration, when exhaust gas in the catalystdownstream side space 29 moves toward the sensor opening 190 b,particulate materials included in the exhaust gas are deposited betweenthe heat shield case 190 and the exhaust gas downstream side end (cornerportion) of the catalyst inner case 4. Therefore, as compared with astructure in which the sensor opening 190 b directly opens toward thecatalyst downstream side space 29, it is possible to largely reduce anamount of particulate materials deposited on the sensor opening 190 bitself (edge portion). An inflow pressure of exhaust gas of the sensoropening 190 b can be maintained at a predetermined pressure or lower.

Especially as compared with a region of the sensor opening 190), aregion of the upstream side gap 23 a formed over the entire peripherybetween the catalyst inner case 4 and the heat shield case 190 can bemade large. Therefore, even if particulate materials are deposited on aportion of the upstream side gap 23 a between the catalyst inner case 4and the heat shield case 190, exhaust gas is supplied to the sensoropening 190 b from other portions (portions of the upstream side gapwhere particulate materials are not deposited). That is, the dieselengine 70 can be continuously operated for a long time until particulatematerials are deposited on the entire region of the upstream side gap 23a which is formed over the entire periphery between the catalyst innercase 4 and the heat shield case 190. An interval between maintenanceoperations for removing particulate materials deposited on the sensoropening 190 b can be set long. Although the diesel engine 70 can becontinuously operated for a long time, a precise state of thedifferential pressure sensor 63 can be maintained for a long time.

1-9. Summary of First Embodiment

As apparent from the above description and FIGS. 1, 9, and 12, theexhaust gas purification device 1 includes two gas purification bodies 2and 3 which purify exhaust gas discharged from the engine 70, the innercases 4, and 20 in which the purification bodies 2 and 3 areincorporated, and the outer cases 5 and 21 in which the inner cases 4and 20 are incorporated, and the outer cases 5 and 21 are arranged sideby side in the exhaust gas moving direction and connected to each other,one of the adjoining inner cases 4 and 20 is inserted into the otherinner case to form a double-layer structure, and the loosely-fitting gap23 is formed between the inner side surface of the one inner case 4 (20)and the outer side surface of the other inner case 20 (4). Therefore,the gas purification body 3 (2) in the other inner case 20 (4) can belargely exposed to outside by separating the other inner case 20 (4)from the one inner case 4 (20). Hence, there is an effect that it ispossible to enhance the operability of the maintenance operation(cleaning and the like of the gas purification bodies 2 and 3) which iscarried out while separating the outer cases 5 and 21 from each other.Both the inner cases 4 and 20 can be easily attached to and detachedfrom each other due to the existence of the loosely-fitting gap 23located between both the inner cases 4 and 20. That is, according to theconventional configuration in which both the inner cases are tightlyfitted to each other to prevent exhaust gas from leaking, both the innercases are integrated due to rust and they cannot be easily separatedfrom each other. In contrast, according to this embodiment, it isextremely easy to separate both the inner cases 4 and 20 from eachother, and there is a merit that this point also enhances themaintenance performance and the exchanging operability of the gaspurification bodies 2 and 3.

As apparent from the above description and FIGS. 1 and 9, the outer sidesurfaces of the inner cases 4 and 20 are provided with the bondingflanges 25 and 26 protruding radially outward, one ends of the outercases 5 and 21 in the exhaust gas moving direction are fixed to thesteps 25 a and 26 a formed on the bonding flanges 25 and 26, and theadjoining bonding flanges 25 and 26 are superposed on each other andthey are detachably connected to each other. Therefore, the outer cases5 and 21 can be easily positioned with respect to the bonding flanges 25and 26 due to existence of the steps 25 a and 26 a. When the outer cases5 and 21 and the bonding flanges 25 and 26 are fixed to each other, itis possible to prevent the outer peripheries of the bonding flanges 25and 26 from interfering with the fixing jigs such as the welding torchand the welding rod, and the machining operability of the outer cases 5and 21 and the bonding flanges 25 and 26 can be enhanced.

As apparent from the above description and FIGS. 1 and 9, the innercases 4 and 20 are supported by the outer cases 5 and 21 in the statewhere the inner cases 4 and 20 are not in direct contact with the outercases 5 and 21 due to the existence of the bonding flanges 25 and 26.Therefore, mechanical vibration and a deforming force externally appliedto the catalyst outer cases 5 and 21 are less prone to be transmitted tothe inner cases 4 and 20, and it is possible to prevent the inner cases4 and 20 themselves and the gas purification bodies 2 and 3 therein frombeing damaged, and to prevent the gas purification bodies 2 and 3 fromdeviating in position. Since the outer cases 5 and 21 are fitted overthe entire outer peripheral regions of the inner cases 4 and 20, theheat insulation layer (heat insulation region) can be secured over theentire outer peripheral regions of the inner cases 4 and 20. Hence, itis possible to reliably prevent the reduction in temperature of exhaustgas in the inner cases 4 and 20. It is also possible to prevent theincrease in surface temperatures of the outer cases 5 and 21. The samefunction effects can be similarly obtained in modifications of the DPF 1shown in FIGS. 16 and 17. According to the modification shown in FIG.16, the adjoining inner cases 4 and 20 are not inserted, the bondingflanges 25 and 26 (40, 41) are superposed on each other and detachablyconnected to each other. In a DPF 1 according to the modification shownin FIG. 17, the heat shield case 190 is omitted, the inner diameter ofthe catalyst inner case 4 is set greater than the outer diameter of thefilter inner case 20, and the exhaust gas upstream side of the filterinner case is inserted into the exhaust gas downstream side of thecatalyst inner case 4.

As shown in the above description and FIGS. 1, 9, 12, and 14, the sensorboss bodies 110 and 113 for supporting the exhaust gas sensors 109, 112,and 63 are provided on the outer side surface of one of the adjoininginner cases 4 and 20. The sensor boss bodies 110 and 113 projectradially outward from the boss body through holes 5 a and 21 a formed inthe outer cases 5 and 21, and the collar 194 which surrounds the sensorboss bodies 110 and 113 and closes the boss body through holes 5 a and21 a is fixed to the outer side surface of the one inner cases 4, 20.Therefore, it is possible to enhance the connection strength between theouter cases 5 and 21 and the inner cases 4 and 20 due to the existenceof the collar 194. Further, it is possible to easily and reliablyprevent the exhaust gas in the inner cases 4 and 20 from leaking fromthe boss body through holes 5 a and 21 a.

Further, as compared with the conventional structure in which one of theinner cases is provided with the diameter-enlarged portion to tightlyfit both the inner cases to each other, distances between the endsurfaces of the gas purification bodies 2 and 3 and the mountingpositions of the exhaust gas sensors 109, 112, and 63 can be set to theshortest distances (zero or arbitrary sizes) without being influenced bypipe-spreading margins of the inner cases 4 and 20 and radii and weldingmargins of the sensor boss bodies 110 and 113. As a result, the entirelength of the DPF 1 can be shortened, and the DPF 1 can be easilyprovided in various kinds of devices. Since the exhaust gas sensors 109,112, and 63 can be close to the end surfaces of the gas purificationbodies 2 and 3 until the sensors come into contact with the end surfacesof the gas purification bodies 2 and 3. Therefore, control performancesuch as automatic regeneration of the DPF 1 can be enhanced.

As apparent from the above description and FIGS. 13 and 14, the pipe 68of the differential pressure sensor 63 as the exhaust gas sensor isconnected to the sensor boss body 113, and the pipe 68 extends along theouter side surfaces of the outer cases 5 and 21. Therefore, the pipe 68is close to the outer side surfaces of the outer cases 5 and 21. Hence,when the DPF 1 is assembled into the engine 70, the pipe 68 does nothinder so much, and the handling performance and mounting performance ofthe DPF 1 are excellent. Therefore, it is easy to carry out the mountingand assembling operations of the DPF 1.

2. Second Embodiment

FIGS. 18 to 34 show a second embodiment of the invention of theapplication. The second embodiment is different from the firstembodiment in the structures of the exhaust gas inlet pipe 16 and thesilencer 30 but is basically the same as the first embodiment.Differences from the first embodiment will be mainly described below.

2-1. Outline Structure of DPF

As shown in FIGS. 18 and 31 to 34, a DPF 1 of the second embodiment isformed into a substantially cylindrical shape extending in the lateraldirection which is in parallel to an output shaft (crankshaft) of adiesel engine 70. The DPF 1 is disposed on an exhaust manifold 71 of theengine 70. An exhaust gas inlet pipe 16 (exhaust gas intake side) and anexhaust gas outlet pipe 34 (exhaust gas downstream side) are provided onright and left sides of the DPF 1 (one end side and the other end sideof moving direction of exhaust gas), i.e., on right and left sides ofthe diesel engine 70. The exhaust gas inlet pipe 16 which is the exhaustgas intake side of the DPF 1 is detachably fastened to the exhaustmanifold 71 of the diesel engine 70 through a bolt. A tail pipe (notshown) is connected to the exhaust gas outlet pipe 34 which is theexhaust gas downstream side of the DPF 1.

As shown in FIGS. 18 to 21, a diesel oxidation catalyst 2 such asplatinum and a soot filter 3 of a honeycomb structure are arranged inseries and accommodated in a DPF casing 60 made of heatproof metalmaterial through cylindrical inner cases 4 and 20. As shown in FIGS. 14to 17, the DPF 1 is mounted on a cylinder head 72 and an exhaustmanifold 71 of the diesel engine 70 through flange-side bracket legs 61a and 61 b and casing-side bracket legs 62 a and 62 b as support bodies.

In this case, base ends of the flange-side bracket legs 61 a and 61 bare detachably fastened, through bolts, to a filter-side bonding flange26 (details thereof will be described later) located on the outerperiphery side of the DPF casing 60. A base end of the casing-sidebracket leg 62 a is integrally welded and fixed to the exhaust gas inletpipe 16 located on the outer periphery side of the DPF casing 60. A baseend of the other casing-side bracket leg 62 b is detachably fastened toan outer lid body 9 (details thereof will be described later) throughbolts. Tip ends of the flange-side bracket legs 61 a and 61 b aredetachably fastened, through bolts, to a side surface of the cylinderhead 72 on the side of a cooling fan 76 and a surface of the cylinderhead 72 on the side of the exhaust manifold 71. A tip end of the onecasing-side bracket leg 62 a is detachably fastened to a side surface ofthe exhaust manifold 71 through a bolt. A tip end of the othercasing-side bracket leg 62 b is detachably fastened to a side surface ofthe cylinder head 72 on the side of the flywheel housing 78 through abolt.

An inlet flange body 17 (details thereof will be described later) of theexhaust gas inlet pipe 16 is fastened to the exhaust gas dischargingside of the exhaust manifold 71. According to this configuration, theDPF 1 is communicated with and connected to the exhaust manifold 71through the exhaust gas inlet pipe 16. As a result, the DPF 1 is stablyconnected to and supported by the exhaust manifold 71 and the cylinderhead 72 which are high rigid parts of the diesel engine 70 by thebracket legs 61 a, 61 b, 62 a, and 62 b. Therefore, it is possible toprevent the DPF 1 from being damaged by vibration.

2-2. Structure of Diesel Oxidation Catalyst

Next, a structure of the diesel oxidation catalyst 2 will be describedwith reference to FIGS. 18, 22, and 26 and the like. As shown in FIGS.18, 22, 26 and 27, the exhaust gas inflow opening 12 formed in thecatalyst inner case 4 and the catalyst outer case 5 opens in arectangular form. Four corners of the exhaust gas inflow opening 12 areformed into are shapes. That is, the four corners 12 a of the exhaustgas inflow opening 12 are rounded. According to this configuration, theexhaust gas inflow opening 12 opens in the rectangular form, and theopening area is made as wide as possible. Therefore, although the inflowresistance of exhaust gas is prevented from increasing, since the fourcorners 12 a are formed into the arc shapes, it is possible to preventthe disturbed flow of exhaust gas passing through the exhaust gas inflowopening 12. Therefore, variation of inflow pressure of exhaust gaspassing through the exhaust gas inflow opening 12 is reduced, and it ispossible to flow the exhaust gas into the exhaust gas inflow opening 12as uniform as possible.

As shown in FIGS. 18, 22 and 26, the exhaust gas inlet pipe 16 isdisposed in the outer side surface of the catalyst outer case 5 in whichthe exhaust gas inflow opening 12 is formed. The exhaust gas inlet pipe16 is formed into a semi-cylindrical shape which opens upward, and iswelded and fixed to the outer side surface of the catalyst outer case 5such that a rectangular upwardly opening end 16 b which is on a largediameter side covers the exhaust gas inflow opening 12, and extends in alongitudinal (lateral) direction of the catalyst outer case 5.Therefore, the upwardly opening end 16 h which is the exhaust gasdownstream side of the exhaust gas inlet pipe 16 is communicated withand connected to the exhaust gas inflow opening 12 of the catalyst outercase 5. A perfect circular downwardly opening end 16 a having a smalldiameter opens, as an exhaust gas intake side, in a right end of theexhaust gas inlet pipe 16 which is closer to a halfway portion of thecatalyst outer case 5 in the longitudinal direction, and the inletflange body 17 is welded and fixed to an outer periphery of thedownwardly opening end 16 a. The inlet flange body 17 is detachablyfastened to the exhaust gas downstream side of the exhaust manifold 71through a bolt.

As shown in FIGS. 18, 22, and 26, a left end of the exhaust gas inletpipe 16 covers the exhaust gas inflow opening 12 of the catalyst outercase 5 from outside. The downwardly opening end 16 a as an exhaust gasinlet side is formed on a right end of the exhaust gas inlet pipe 16.That is, the downwardly opening end 16 a of the exhaust gas inlet pipe16 is provided on the substantially rectangular exhaust gas inflowopening 12 such that the downwardly opening end 16 a is deviated towardthe exhaust gas downstream side (downwardly opening end 16 a is deviatedrightward from catalyst outer case 5 in position). The upwardly openingend 16 b of the exhaust gas inlet pipe 16 is welded and fixed to theouter side surface of the catalyst outer case 5 such that the upwardlyopening end 16 b covers the exhaust gas inflow opening 12 and extends inthe longitudinal (lateral) direction of the catalyst outer case 5.Hence, an introducing passage 200 of exhaust gas is formed by an outerside surface of the catalyst outer case 5 and an inner side surface ofthe exhaust gas inlet pipe 16.

As shown in FIGS. 18, 22, and 26, at least one of the outer side surfaceof the catalyst outer case 5 and the inner side surface of the exhaustgas inlet pipe 16 is provided with rectifier fins 201 a and 201 b asrectifiers which rectify flow of exhaust gas. The rectifier fins 201 aand 201 b are formed into curved pieces. In this embodiment, theupstream side rectifier fin 201 a located on the exhaust gas upstreamside is welded and fixed to the outer side surface of the catalyst outercase 5. The downstream side rectifier fin 201 b located on the exhaustgas downstream side is welded and fixed to the inner side surface of theexhaust gas inlet pipe 16. Both the rectifier fins 201 a and 201 b aredeviated from each other so that they are not superposed on each otherin a state where the exhaust gas inlet pipe 16 is welded and fixed tothe outer side surface of the catalyst outer case 5. The upstream siderectifier fin 201 a guides, in the longitudinal direction of the exhaustgas inlet pipe 16, exhaust gas which flows into the downwardly openingend 16 a of the exhaust gas inlet pipe 16. The downstream side rectifierfin 201 b guides exhaust gas in the introducing passage 200 toward theexhaust gas inflow space 11 through the exhaust gas inflow opening 12.Exhaust gas which flows from the exhaust manifold 71 into the exhaustgas inlet pipe 16 forms a substantially S-shaped flow as viewed fromside by existence of both the rectifier fins 201 a and 201 b, and theexhaust gas is sent into the exhaust gas inflow opening 12.

According to this configuration, since exhaust gas can be smoothly sentinto the DPF 1 by existence of both the rectifier fins 201 a and 201 bwithout being largely influenced by the shape of the exhaust gas inletpipe 16. Therefore, it is possible to flow exhaust gas into the exhaustgas inflow space 11 and thus, into the diesel oxidation catalyst 2 asuniform as possible, and the entire region of the diesel oxidationcatalyst 2 can be efficiently utilized. The upstream side rectifier fin201 a is welded and fixed to the outer side surface of the catalystouter case 5 and the downstream side rectifier fin 201 b is welded andfixed to the inner side surface of the exhaust gas inlet pipe 16 basedon the assumption that the introducing passage 200 is formed by theouter side surface of the catalyst outer case 5 and the inner sidesurface of the exhaust gas inlet pipe 16. Therefore, although therectifier fins 201 a and 201 b are located in the exhaust gasintroducing passage 200, both the rectifier fins 201 a and 201 b can bemounted by a simple machining operation.

2-3. Structure of Soot Filter

Next, a structure of the soot filter 3 will be described with referenceto FIGS. 18, 22 and 26. The soot filter 3 is provided in a substantiallycylindrical filter inner case 20 made of heatproof metal material. Thefilter inner case 20 is provided in a substantially cylindrical filterouter case 21 made of heatproof metal material. That is, the filterinner case 20 is fitted over the soot filter 3 through a mat-shapedfilter heat insulator 22 made of ceramic fiber. The filter outer case 21is one of elements constituting the DPF casing 60 together with thecatalyst outer case 5. The soot filter 3 is protected by press-fittingthe filter heat insulator 22 between the soot filter 3 and the filterinner case 20.

As shown in FIGS. 18, 22, and 26, the catalyst inner case 4 is acylindrical in shape having a straight ridge line and includes anupstream side cylindrical portion 4 a in which the diesel oxidationcatalyst 2 is accommodated and a downstream side cylindrical portion 4 binto which the later-described filter inner case 20 is inserted. Theupstream side cylindrical portion 4 a and the downstream sidecylindrical portion 4 b are cylinders having substantially the samediameters and are integrally formed. The catalyst inner case 4 furtherincludes a thin ring-like catalyst-side bonding flange 25 which iswelded and fixed to an outer periphery of the catalyst inner case 4, anda thin ring-like filter-side bonding flange 26 which is welded and fixedto an outer periphery of the filter inner case 20. The catalyst-sidebonding flange 25 and the filter-side bonding flange 26 are formed intodoughnut shapes having substantially L-shaped cross sections.

An inner periphery of the catalyst-side bonding flange 25 is welded andfixed to an end of the downstream side cylindrical portion 4 b of thecatalyst inner case 4. The outer periphery of the catalyst-side bondingflange 25 projects toward the outer periphery (radial direction) of thecatalyst outer case 5. A bent angle portion of the catalyst-side bondingflange 25 is a step-wise step 25 a. An exhaust gas-downstream side endof the catalyst outer case 5 is welded and fixed to the step 25 a of thecatalyst-side bonding flange 25. An inner periphery of the filter-sidebonding flange 26 is welded and fixed to a longitudinally halfwayportion (halfway portion in moving direction of exhaust gas) of theouter periphery of the filter inner case 20. An outer periphery of thefilter-side bonding flange 26 projects toward the outer periphery(radial direction) of the filter outer case 21. A bent angle portion ofthe filter-side bonding flange 26 is also formed into a step-wise step26 a. An exhaust gas upstream side end of the filter outer case 21 iswelded and fixed to the step 26 a of the filter-side bonding flange 26.The filter inner case 20 is a cylindrical in shape having a straightridge line. The exhaust gas upstream side end and the exhaust gasdownstream side end of the filter inner case 20 are cylinders havingsubstantially the same diameters and integrally formed.

An outer diameter of the diesel oxidation catalyst 2 and an outerdiameter of the soot filter 3 are equal to each other. A thickness ofthe catalyst heat insulator 6 is greater than that of the filter heatinsulator 22. The catalyst inner case 4 and the filter inner case 20 areformed from material having the same thickness. An outer diameter of thefilter inner case 20 is smaller than an inner diameter of the downstreamside cylindrical portion 4 b of the catalyst inner case 4. A downstreamside gap 23 is formed between the inner peripheral surface of thecatalyst inner case 4 and the outer peripheral surface of the filterinner case 20. The downstream side gap 23 has a size (e.g., 2 mm) whichis greater than thicknesses (e.g., 1.5 mm) of the cases 4 and 20.According to this configuration, even if the cases 4 and 20 become rustyor thermally deformed, the exhaust gas upstream side end of the filterinner case 20 can be easily put into or pulled out from the downstreamside cylindrical portion 4 b of the catalyst inner case 4.

As shown in FIGS. 18 to 22 and 25, the catalyst-side bonding flange 25and the filter-side bonding flange 26 are butted against each otherthrough a gasket 24. The bonding flanges 25 and 26 are sandwiched fromboth sides in the moving direction of exhaust gas by a pair of thickcentral grasping flanges 51 and 52 which surround outer peripheries ofthe outer cases 5 and 21. The central grasping flanges 51 and 52 arefastened to each other through bolt 27 and nut 28 to sandwich thebonding flanges 25 and 26 between the central grasping flanges 51 and52. According to this configuration, the catalyst outer case 5 and thefilter outer case 21 are detachably connected to each other.

As shown in FIGS. 18 and 25, in a state where the exhaust gas upstreamside end of the filter outer case 21 is connected to the exhaustgas-downstream side end of the catalyst outer case 5 through the centralgrasping flanges 51 and 52 and the bonding flanges 25 and 26, a catalystdownstream side space 29 is formed between the diesel oxidation catalyst2 and the soot filter 3. That is, a gas outflow end surface 2 b of thediesel oxidation catalyst 2 and an intake side end surface 3 a of thesoot filter 3 (filter inner case 20) are opposed to each other at asensor mounting distance L2 from each other.

As shown in FIGS. 18 and 22, a cylinder length L4 of the catalyst outercase 5 in the exhaust gas moving direction is longer than a cylinderlength L3 of the upstream side cylindrical portion 4 a of the catalystinner case 4 in the exhaust gas moving direction. A cylinder length L6of the filter outer case 21 in the exhaust gas moving direction isshorter than a cylinder length L5 of the filter inner case 20 in theexhaust gas moving direction. A total length (L2+L3+L5) of the sensormounting distance L2 of the catalyst downstream side space 29, thecylinder length L3 of the upstream side cylindrical portion 4 a of thecatalyst inner case 4, and the cylinder length L5 of the filter innercase 20 is substantially equal to a total length (L4+L6) of the cylinderlength L4 of the catalyst outer case 5 and the cylinder length L6 of thefilter outer case 21.

The exhaust gas upstream side end of the filter inner case 20 projectsfrom the exhaust gas upstream side end of the filter outer case 21 by alength difference (L7≈L5−L6) between the cases 20 and 21. Hence, in astate where the filter outer case 21 is connected to the catalyst outercase 5, the exhaust gas upstream side end of the filter inner case 20 isinserted into the exhaust gas-downstream side of the catalyst outer case5 (downstream side cylindrical portion 4 b of catalyst inner case 4) bythe upstream side size L7 of the filter inner case 20 projecting fromthe filter outer case 21. That is, the exhaust gas upstream side of thefilter inner case 20 is inserted into the downstream side cylindricalportion 4 b (catalyst downstream side space 29) such that the exhaustgas upstream side of the filter inner case 20 can be pulled out. As canbe found from the above description and FIG. 1, a flange body(catalyst-side bonding flange 25 and filter-side bonding flange 26)which connects the catalyst outer case 5 and the filter outer case 21 toeach other is deviated from a connection boundary position (catalystdownstream side space 29) between the diesel oxidation catalyst 2 andthe soot filter 3. In other words, mounting positions of thecatalyst-side bonding flange 25 and the filter-side bonding flange 26are deviated from the catalyst downstream side space 29.

2-4 Structure of Silencer

Next, a structure of the silencer 30 will be described with reference toFIGS. 18, 22, and 28. As shown in FIGS. 18, 22, and 28, the silencer 30which reduces sound of exhaust gas discharged from the diesel engine 70includes a substantially cylindrical silencing inner case 31 made ofheatproof metal material, a substantially cylindrical silencing outercase 32 made of heatproof metal material, and a disk-like side lid body33 fixed to an exhaust gas downstream side end of the silencing outercase 32 by welding. The silencing inner case 31 is provided in thesilencing outer case 32. The silencing outer case 32 forms the DPFcasing 60 together with the catalyst outer case 5 and the filter outercase 21. A diameter of the cylindrical silencing outer case 32 issubstantially equal to those of the cylindrical catalyst outer case 5and the cylindrical filter outer case 21.

A disk-like inner lid body 36 is fixed to a halfway portion in thesilencing inner case 31 by welding. A pair of exhaust gas introducingpipes 38 extending in parallel to the exhaust gas moving direction isprovided in the silencing inner case 31. An exhaust gas upstream side ofeach of the exhaust gas introducing pipes 38 penetrates an upstreaminner lid body 36 and projects into the filter inner case 20 (filterdownstream side space 49, details thereof will be described later). Theexhaust gas upstream side end of each of the exhaust gas introducingpipes 38 is closed by the downstream inner lid body 37. A large numberof communication holes 39 are formed in each of the exhaust gasintroducing pipes 38. The communication holes 39 are also formed in theexhaust gas introducing pipe 38 at location closer to the exhaust gasupstream side than the upstream inner lid body 36. Each of the exhaustgas introducing pipes 38 is in communication with an expansion chamber45 through the communication holes 39. The expansion chamber 45 isformed in the silencing inner case 31 (between upstream inner lid body36 and side lid body 33).

The exhaust gas outlet pipe 34 disposed between the exhaust gasintroducing pipes 38 penetrates the side lid body 33 of the silencingouter case 32. The exhaust gas upstream side of the exhaust gas outletpipe 34 is closed by the inner lid body 36. A large number of exhaustholes 46 are formed in a portion of the exhaust gas outlet pipe 34located in the silencing inner case 31. The exhaust gas introducingpipes 38 are in communication with the exhaust gas outlet pipe 34through the large number of communication holes 39, the expansionchamber 45 and the large number of exhaust gas holes 46. A tail pipe(not shown) is connected to the other end of the exhaust gas outlet pipe34. In the above-described configuration, exhaust gas which enters eachof the exhaust gas introducing pipes 38 of the silencing inner case 31passes through the exhaust gas outlet pipe 34 through the plurality ofcommunication holes 39, the expansion chamber 45, and the large numberof exhaust gas holes 46, and is discharged from the silencer 30 throughthe tail pipe.

As shown in FIGS. 18, 22, 28, and 29, an inner diameter side of the thinring-like filter outlet-side bonding flange 40 is welded and fixed tothe exhaust gas downstream side end of the filter inner case 20. Anouter diameter side of the filter outlet-side bonding flange 40protrudes toward an outer periphery (radial direction, radially outwarddirection) of the filter outer case 21. The exhaust gas downstream sideend of the filter outer case 21 is welded and fixed to the outerperiphery of the filter outlet-side bonding flange 40. A thinsilencing-side bonding flange 41 protruding toward the outer periphery(radially outward) of the silencing outer case 32 is welded and fixed tothe exhaust gas upstream side end of the silencing inner case 31. Theexhaust gas upstream side end of the silencing outer case 32 is weldedand fixed to the outer periphery of the silencing-side bonding flange41. The exhaust gas upstream side end of the silencing inner case 31projects toward the exhaust gas upstream side of the silencing-sidebonding flange 41 by a predetermined cylinder size L10. The filter innercase 20 and the silencing inner case 31 are cylinders havingsubstantially the same diameters, and the filter outer case 21 and thesilencing outer case 32 are cylinders having substantially the samediameters.

As shown in FIGS. 18 to 21 and 23, the filter outlet-side bonding flange40 and the silencing-side bonding flange 41 are abutted against eachother through the gasket 24, and the bonding flanges 40 and 41 aresandwiched from both sides in the exhaust gas moving direction by a pairof thick outlet grasping flanges 53 and 54 which surround outerperipheries of the outer cases 21 and 32. The outlet grasping flanges 53and 54 are fastened to the bonding flanges 40 and 41 through bolts 42and nuts 43. According to this operation, the filter outer case 21 andthe silencing outer case 32 are detachably connected to each other.

As shown in FIGS. 18 and 22, a cylinder length L9 of the silencing outercase 32 in the exhaust gas moving direction is shorter than a cylinderlength L8 of the silencing inner case 31 in the exhaust gas movingdirection. The exhaust gas upstream side end of the silencing inner case31 projects from the exhaust gas upstream side end (bonding flange 41)of the silencing outer case 32 by a length difference (L10≈L8−L9)between the cases 31 and 32. That is, in a state where the silencingouter case 32 is connected to the filter outer case 21, the exhaust gasupstream side end of the silencing inner case 31 is inserted into thefilter downstream side space 49 formed in the exhaust gas downstreamside end (filter outlet-side bonding flange 40) of the filter outer case21 by the size L10 by which the upstream side end of the silencing innercase 31 projects. Especially in this embodiment, the exhaust gasupstream side end of each of the exhaust gas introducing pipes 38projects forward of the exhaust gas upstream side end of the silencinginner case 31 (toward the exhaust gas upstream side). That is, theexhaust gas upstream side of each of the exhaust gas introducing pipes38 enters the filter inner case 20 (see FIGS. 18, 22, 28 and 29). As canbe found from the above description and FIG. 18, the flange bodies(filter outlet-side bonding flange 40 and the silencing-side bondingflange 41) which connect the filter outer case 21 and the silencingouter case 32 are deviated from the connection boundary position (filterdownstream side space 49) of the soot filter 3. In other words, themounting positions of the filter outlet-side bonding flange 40 and thesilencing-side bonding flange 41 are deviated from the filter downstreamside space 49.

According to this configuration, the length of each of the exhaust gasintroducing pipes 38 in the exhaust gas moving direction can be secured,and the length of the silencer 30 (silencing outer case 32) in theexhaust gas moving direction can be shortened. Therefore, the entire DPF1 having the silencer 30 can be made compact and the silencing functionof the silencer 30 can be maintained and enhanced. Especially in thisembodiment, the halfway portion in the silencing inner case 31 is closedby the disk-like inner lid body 36, the inner lid body 36 penetrates theexhaust gas upstream side of the exhaust gas introducing pipe 38, andthe communication holes 39 are also formed in the exhaust gasintroducing pipe 38 at location closer to exhaust gas upstream than theinner lid body 36. The communication holes 39 closer to the exhaust gasupstream side than the inner lid body 36 contributes to a taking-inoperation into the silencer 30. Hence, the length of the silencer 30(silencing outer case 32) in the exhaust gas moving direction can beshortened, the moving distance of the exhaust gas itself can besufficiently secured, and the silencing function of the silencer 30 canbe further enhanced.

2-5. Connecting Structure of Adjoining Outer Cases

The connecting structure of the adjoining outer cases 5, 21, and 32 willbe described with reference to FIGS. 18 to 21 and 23. In the secondembodiment, like the first embodiment, the exhaust gas purificationdevice includes the gas purification bodies 2 and 3 which purify exhaustgas discharged from the engine 70, the inner cases 4, 20, and 31 inwhich the gas purification bodies 2 and 3 are incorporated, and theouter cases 5, 21, and 32 in which the inner cases 4, 20, and 31 areincorporated. The inner cases 4, 20, and 31 are connected to the outercases 5, 21, and 32 through the bonding flanges 25, 26, 40, and 41 whichprotrudes toward outer peripheries of the outer cases 5, 21, and 32. Theconnecting structure includes a plurality of sets of a combination ofthe gas purification bodies 2 and 3, the inner cases 4, 20, and 31 andthe outer cases 5, 21, and 32. The bonding flanges 25 and 26 (40, 41)are sandwiched between and fixed by the pair of grasping flanges 51 and52 (53, 54), thereby connecting the plurality of outer cases 5, 21, and32 to each other.

Therefore, the adjoining bonding flanges 25 and 26 (40, 41) can besandwiched from both sides by the grasping flanges 51 and 52 (53, 54)and can be (tightly) connected to each other under pressure. Further,substantially uniform pressure contacting force can be applied to theentire bonding flanges 25 and 26 (40, 41), and high surface pressure ofthe sealing surfaces (sandwiching surfaces) of the grasping flanges 51to 54 can be maintained. As a result, it is possible to reliably preventexhaust gas from leaking between the bonding flanges 25 and 26 (40, 41).Although the grasping flanges 51 to 54 are formed from the plurality ofsemi-arc bodies 51 a and 51 b (52 a, 52 b, 53 a, 53 b, 54 a, 54 b), theycan be assembled in the same manner as one integral member as in thefirst embodiment.

2-6. Details of Structure of Bonding Flange

Next, a detailed structure of the bonding flanges 25, 26 and 40 will bedescribed. Since the bonding flanges 25, 26, and 40 basically have thesame structures, the catalyst-side bonding flange 25 which is welded andfixed to the catalyst inner case 4 and the catalyst outer case 5 will bedescribed as a representative example with reference to FIG. 24. Asshown in FIG. 24, the step-wise step 25 a is formed on the bent angleportion of the catalyst-side bonding flange 25. The exhaust gasdownstream side end of the catalyst outer case 5 is fitted over the step25 a, and the step 25 a is welded and fixed to the exhaust gasdownstream side end of the catalyst outer case 5.

An L-shaped inner diameter-side end 25 b in the catalyst-side bondingflange 25 extends in the exhaust gas moving direction of the catalystinner case 4 (catalyst outer case 5). The inner diameter-side end 25 bis fitted over the exhaust gas downstream side end of the catalyst innercase 4, and is welded and fixed to the catalyst inner case 4. AnL-shaped outer diameter-side end 25 c in the catalyst-side bondingflange 25 extends in the radial direction (vertical direction) from theouter periphery of the catalyst outer case 5. High rigidity of thecatalyst-side bonding flange 25 is secured due to the existence of theL-shaped cross section of the catalyst-side bonding flange 25 and thestep 25 a.

The nuts 28 are threadedly engaged with the bolts 27 which pass throughthe bolt holes 56 in the grasping flanges 51 and 52 and the bondingflanges 25 and 26, thereby fastening the grasping flanges 51 and 52 andthe bonding flanges 25 and 26 to each other, and the outer diameter-sideend 25 c of the catalyst-side bonding flange 25 is sandwiched betweenthe grasping flanges 51 and 52 as described above.

2-7. Mounting Structure of Gas Temperature Sensor

Next, the gas temperature sensors 109 and 112 provided in the DPF 1 willbe described with reference to FIGS. 18, 25, 26, 28 and 29. As shown inFIGS. 18, 25, and 26, one end of a cylindrical sensor boss body 110 iswelded and fixed to a portion of the outer peripheral surface of thecatalyst inner case 4 located between the upstream side cylindricalportion 4 a and the downstream side cylindrical portion 4 b. The otherend of the sensor boss body 110 extends in the radial direction towardan outer side of the catalyst outer case 5 from a sensor mountingopening 5 a of the catalyst outer case 5. That is, the sensor boss body110 for supporting the exhaust gas sensor is provided at a portion ofthe outer peripheral surface of the catalyst inner case 4 which is inthe vicinity of the connection boundary position (catalyst downstreamside space 29) between the diesel oxidation catalyst 2 and the sootfilter 3 such that the sensor boss body 110 penetrates the catalystouter case 5. The sensor mounting bolt 111 is threadedly engaged withthe other end of the sensor boss body 110. The sensor mounting bolt 111penetrates, for example, the thermistor-shaped upstream side gastemperature sensor 109 and the upstream side gas temperature sensor 109is supported by the sensor boss body 110 through the sensor mountingbolt 111. A detecting portion of the upstream side gas temperaturesensor 109 projects into the catalyst downstream side space 29. In theabove-described configuration, if exhaust gas is discharged from the gasoutflow end surface 2 b of the diesel oxidation catalyst 2, atemperature of the exhaust gas is detected by the upstream side gastemperature sensor 109.

As shown in FIGS. 25 and 26, the sensor boss body 110 on the exhaust gasupstream side is located on an extension of the gas outflow end surface2 b which intersects with the exhaust gas moving direction at rightangles in the diesel oxidation catalyst 2 and on an extension of theintake side end surface 3 a which intersects with the exhaust gas movingdirection at right angles in the soot filter 3. In this case, adisposition distance between the gas outflow end surface 2 b of thediesel oxidation catalyst 2, the intake side end surface 3 a of the sootfilter 3, and the upstream side gas temperature sensor 109 can be setextremely short (they can be disposed closely). Therefore, the entireDPF 1 can be made compact, the detection precision of the upstream sidegas temperature sensor 109 can be enhanced, and performance such as theregeneration control of the DPF 1 can be enhanced.

As shown in FIGS. 18, 28, and 29, one end of the cylindrical sensor bossbody 110 is also welded and fixed to a portion of the outer peripheralsurface of the filter inner case 20 which is in the vicinity of thefilter downstream side space 49. The other end of the sensor boss body110 extends from the sensor mounting opening 21 a of the filter outercase 21 in the radial direction toward the outer side of the filterouter case 21. That is, the sensor boss body 110 for supporting theexhaust gas sensor is provided at a portion of the outer peripheralsurface of the filter inner case 20 which is in the vicinity of theconnection boundary position of the soot filter 3 such that the sensorboss body 110 penetrates the filter outer case 21. The sensor mountingbolt 111 is threadedly engaged with the other end of the sensor bossbody 110. The sensor mounting bolt 111 penetrates, for example, thethermistor-shaped downstream side gas temperature sensor 112, and thedownstream side gas temperature sensor 112 is supported by the sensorboss body 110 through the sensor mounting bolt 111. A detecting portionof the downstream side gas temperature sensor 112 projects into thefilter downstream side space 49. In the above configuration, if exhaustgas is discharged from the discharge side end surface 3 b of the sootfilter 3, a temperature of the exhaust gas is detected by the downstreamside gas temperature sensor 112.

As shown in FIGS. 28 and 29, the sensor boss body 110 on the exhaust gasdownstream side is located on an extension of the discharge side endsurface 3 b which intersects with the exhaust gas moving direction atright angles in the soot filter 3 and on an extension of the an endsurface (downstream inner lid body 37) on the exhaust gas upstream sidein each of the exhaust gas introducing pipes 38. In this case, adisposition distance between the discharge side end surface 3 b of thesoot filter 3 and the downstream side gas temperature sensor 112 can beset extremely short (they can be disposed closely). In this point also,the entire DPF 1 can be made compact, the detection precision of thedownstream side gas temperature sensor 112 can be enhanced, andperformance such as the regeneration control of the DPF 1 can beenhanced.

The sensor boss body 113 (see FIGS. 31 to 34) of the later-describeddifferential pressure sensor 63 can of course be formed like the sensorboss body 110 with respect to both the gas temperature sensors 109 and112.

2-8. Mounting Structure of Differential Pressure Sensor

Next, the differential pressure sensor 63 provided in the DPF 1 will bedescribed with reference to FIGS. 31 to 34. The differential pressuresensor 63 is for detecting a pressure difference of exhaust gas betweenthe upstream side and downstream side with the soot filter 3therebetween in the DPF 1. The differential pressure sensor 63 is formedsuch that a deposited amount of particulate materials of the soot filter3 is converted based on the pressure difference and the clogged state inthe DPF 1 can be grasped. That is, acceleration control means or intakethrottle control means (both not shown) is operated based on thepressure difference of exhaust gas detected by the differential pressuresensor 63 so that the regeneration of the soot filter 3 can beautomatically controlled.

A sensor bracket 66 is fastened to the outlet grasping flange 54 on thesilencing side through a bolt, and the sensor bracket 66 is disposed onan upper surface of the DPF casing 60. A detecting body 67 of thedifferential pressure sensor 63 is mounted on the sensor bracket 66. Anupstream side pipe joint body 64 and a downstream side pipe joint body65 are connected to a detecting body 67 of the differential pressuresensor 63 through an upstream side sensor pipe 68 and a downstream sidesensor pipe 69. Like the sensor boss body 110, the sensor boss body 113is disposed on the DPF casing 60. The upstream side pipe joint body 64(downstream side pipe joint body 65) is fastened to the sensor boss body113 through pipe joint bolts 114.

2-9. Another Example of Silencer Structure

FIG. 30 shows another example of a structure of the silencer 30. In thiscase, a disk-like inner lid body 36 is fixed to an exhaust gas upstreamside end of the silencing inner case 31 by welding. The exhaust gasupstream side of each of the exhaust gas introducing pipes 38 penetratesthe inner lid body 36, but a position of the exhaust gas upstream sideend of the exhaust gas introducing pipe 38 and a position of the exhaustgas upstream side end of the silencing inner case 31 substantially matchwith each other as viewed from side in cross section. The exhaust gasupstream side end of each of the exhaust gas introducing pipes 38 opensas it is. Other configurations are the same as those of the previousembodiments. According to this configuration also, the length of theexhaust gas introducing pipe 38 in the exhaust gas moving direction canbe secured, the length of the silencer 30 (silencing outer case 32) inthe exhaust gas moving direction can be shortened, the entire DPF 1having the silencer 30 can be made compact, and the silencing functionin the silencer 30 can be maintained and enhanced.

2-10. Summary of Second Embodiment

As apparent from the above description and FIGS. 18, 22, and 26, theexhaust gas purification device 1 includes two gas purification bodies 2and 3 which purify exhaust gas discharged from the engine 70, the innercases 4 and 20 in which the purification bodies 2 and 3 areincorporated, the outer cases 5 and 21 in which the inner cases 4 and 20are incorporated, the exhaust gas inlet pipe 16 into which exhaust gasfrom the engine 70 flows, and the exhaust gas outlet pipe 34 from whichexhaust gas passing through both the gas purification bodies 2 and 3flows out. The outer cases 5 and 21 are arranged side by side in theexhaust gas moving direction and connected to each other. The exhaustgas inlet pipe 16 is mounted on the exhaust gas upstream side outer case5 such that the introducing passage 200 for exhaust gas is formed fromthe outer side surface of the exhaust gas upstream side outer case 5 andthe inner side surface of the exhaust gas inlet pipe 16. The rectifierfins 201 a and 201 b for rectifying the flow of exhaust gas are providedon at least one of the outer side surface of the exhaust gas upstreamside outer case 5 and the inner side surface of the exhaust gas inletpipe 16. Therefore, exhaust gas can be smoothly sent into the exhaustgas purification device 1 without being largely influenced by the shapeof the exhaust gas inlet pipe 16 due to existence of both the rectifierfins 201 a and 201 b. Therefore, there is an effect that it is possibleto flow exhaust gas into the gas purification body 2 on the exhaust gasupstream side as uniformly as possible, and the entire region of the gaspurification body 2 can be efficiently utilized.

As apparent from the above description and FIGS. 18 and 22, the flangebodies 25 and 26 which connect the outer cases 5 and 21 to each otherare deviated from the connection boundary position 29 of the gaspurification bodies 2 and 3. Therefore, it is possible to secure thelengths of the gas purification bodies 2 and 3 in the exhaust gas movingdirection, and to shorten the lengths of both the outer cases 5 and 21in the exhaust gas moving direction. Therefore, there is an effect thatrigidity of each of the outer cases 5 and 21 can be enhanced, weightthereof can be reduced, and the entire length of the exhaust gaspurification device 1 can be made compact (can be shortened). There isalso a merit that it is possible to easily prevent exhaust gas fromleaking due to existence of the bonding flanges 25 and 26.

The flange bodies 40 and 41 which connect the exhaust gas downstreamside outer case 21 and the silencer 30 to each other are deviated fromthe connection boundary position of the gas purification body 3 on theexhaust gas downstream side. Therefore, lengths of the outer case 21 onthe exhaust gas downstream side and the silencer 30 in the exhaust gasmoving direction can be shortened, and the entire length of the exhaustgas purification device 1 having the silencer 30 can be made compact(can be shortened).

As apparent from the above description and FIGS. 18 and 22, the innercase 20 (4) in which the other gas purification body 3 (2) isincorporated is inserted into the inner case 4 (20) of the one gaspurification body 2 (3), and the gap 23 is formed between the innercases 4 and 20. Therefore, by separating the other inner case 20 (4)from the one inner case 4 (20), it is possible to largely expose, tooutside, the gas purification body 3 (2) located in the other inner case20 (4). Hence, there is an effect that the maintenance operation(cleaning and the like of the gas purification bodies 2 and 3) which iscarried out while separating the outer cases 5 and 21 from each other byreleasing the connection between the flange bodies 25 and 26 can beenhanced. Both the inner cases 4 and 20 can be easily attached to anddetached from each other due to the existence of the gap 23 locatedbetween both the inner cases 4 and 20. That is, according to theconventional configuration in which both the inner cases 4 and 20 aretightly fitted to each other to prevent exhaust gas leakage, both theinner cases 4 and 20 are integrated due to rust and they cannot beeasily separated from each other. In contrast, it is extremely easy toseparate both the inner cases 4 and 20 from each other, and this pointalso enhances the maintenance performance and the exchanging operabilityof the gas purification bodies 2 and 3.

As apparent from the above description and FIGS. 18, 22, and 26, therectifier fins 201 a and 201 b are provided on both the outer sidesurface of the outer case 5 on the exhaust gas upstream side and theinner side surface of the exhaust gas inlet pipe 16, the rectifier fin201 a on the side of the outer case 5 is located on the exhaust gasupstream side, and the rectifier fin 201 b on the side of the exhaustgas inlet pipe 16 is located on the exhaust gas downstream side.Therefore, although the rectifier fins 201 a and 201 b are located inthe introducing passage 200, there is an effect that they can be mountedon the outer side surface of the outer case 5 or the exhaust gas inletpipe 16 without interfering with each other by a simple machiningoperation.

As apparent from the above description and FIGS. 18, 22, 26, and 27, theexhaust gas inflow opening 12 which is in communication with the exhaustgas inlet pipe 16 is formed in the outer case 5 on the exhaust gasupstream side and the inner case 4 incorporated in the outer case 5, theexhaust gas inflow opening 12 opens in a rectangular form, and the fourcorners 12 a thereof are formed into arc shapes. Therefore, the exhaustgas inflow opening 12 opens in the rectangular form, and an opening areais made as wide as possible. Hence, although the inflow resistance ofexhaust gas is prevented from increasing, since the four corners 12 aare formed into the are shapes, it is possible to prevent the disturbedflow of exhaust gas passing through the exhaust gas inflow opening 12.Therefore, there is an effect that variation of inflow pressure ofexhaust gas passing through the exhaust gas inflow opening 12 isreduced, and it is possible to flow the exhaust gas into the exhaust gasinflow opening 12 as uniformly as possible.

As apparent from the above description and FIGS. 18, 22, and 28, theexhaust gas purification device includes two gas purification bodies 2and 3 which purify exhaust gas discharged from the engine 70, the innercases 4 and 20 in which the gas purification bodies 2 and 3 areincorporated, and the outer cases 5 and 21 in which the inner cases 4and 20 are incorporated, the exhaust gas inlet pipe 16 into whichexhaust gas from the engine 70 flows, and the exhaust gas outlet pipe 34from which exhaust gas passing through both the purification bodies 2and 3 flows out. The outer cases 5 and 21 are arranged side by side inthe exhaust gas moving direction and connected to each other. Thesilencer 30 having the exhaust gas outlet pipe 34 is mounted on theexhaust gas downstream side outer case 21, the exhaust gas introducingpipe 38 extending in parallel to the exhaust gas moving direction isincorporated in the silencer 30, and the exhaust gas upstream side ofthe exhaust gas introducing pipe 38 enters the exhaust gas downstreamside inner case 20. Therefore, it is possible to secure the length ofthe exhaust gas introducing pipe 38 in the exhaust gas moving direction,and to shorten the length of the silencer 30 (silencing outer case 32)in the exhaust gas moving direction. Therefore, in the exhaust gaspurification device 1 having the silencer 30, there is an effect thatthe entire exhaust gas purification device 1 can be made compact, andthe silencing function of the silencer 30 can be maintained andenhanced.

As apparent from the above description and FIGS. 18, 22, 28 and 29, theexhaust gas upstream side end of the silencer 30 is closed by the innerlid body 36, the exhaust gas introducing pipe 38 penetrates the innerlid body 38 and enters the exhaust gas downstream side inner case 20,and the communication holes 39 for taking in exhaust gas are formed inthe exhaust gas introducing pipe 38 at a location in exhaust gasupstream of the inner lid body 36. The communication holes 39 in exhaustgas upstream of the inner lid body 36 contribute to intake of exhaustgas into the silencer 30. Hence, there is an effect that although thelength of the silencer 30 in the exhaust gas moving direction isshortened, a sufficient moving distance of exhaust gas can be secured,and the silencing function of the silencer 30 can further be enhanced.

As apparent from the above description and FIGS. 18, 25, 26, 28, and 29,the sensor boss body 110 for supporting the exhaust gas sensor 112 isprovided on the outer peripheral surface of the exhaust gas downstreamside inner case 20 which is in the vicinity of the connection boundaryposition 49 of the gas purification body 3 such that the sensor bossbody 110 penetrates the exhaust gas downstream side outer case 21. Thesensor boss body 110 is located on an extension of the end surface 3 bwhich intersects with the exhaust gas moving direction at right anglesin the gas purification body 3, or on an extension of the exhaust gasupstream side end surface in the exhaust gas introducing pipe 38.Therefore, the disposition distance between the end surface 3 b of thegas purification body 3 and the exhaust gas sensor 112 can be setextremely short (they can be disposed closely). Therefore, there iseffect that the entire exhaust gas purification device 1 can be madecompact, detection precision of the exhaust gas sensor 112 can beenhanced, and performance such as the regeneration control of theexhaust gas purification device 1 can be enhanced.

Configurations of various portions in the invention of the applicationare not limited to the embodiments, and the configurations can bevariously changed within a scope not departing from the subject matterof the invention of the application.

REFERENCE SIGNS LIST

-   -   1 DPF (diesel particulate filter)    -   2 Diesel oxidation catalyst (gas purification body)    -   3 Soot filter (gas purification body)    -   4 Catalyst inner case    -   5 Catalyst outer case    -   5 a, 21 a Boss body through hole    -   20 Filter inner case    -   21 Filter outer case    -   25 Catalyst-side bonding flange    -   63 Differential pressure sensor (exhaust gas sensor)    -   70 Diesel engine    -   109, 112 Gas temperature sensor (exhaust gas sensor)    -   110, 113 Sensor boss body

The invention claimed is:
 1. An exhaust gas purification devicecomprising: two gas purification bodies for purifying exhaust gasdischarged from an engine; inner cases for incorporating the gaspurification bodies; outer cases for incorporating the inner cases, theouter cases being arranged side by side in an exhaust gas movingdirection and connected to each other, wherein one of the adjoininginner cases is inserted into the other inner case to form a double-layerstructure, and a loosely-fitting gap is formed between an inner sidesurface of the one inner case and an outer side surface of the otherinner case; and an exhaust gas inlet pipe that receives exhaust gasflowing in from the engine, and an exhaust gas outlet pipe through whichthe exhaust gas flows out after passing through the gas purificationbodies, wherein an upward-facing opening of the exhaust gas inlet pipeis fixed to an outer side surface of the outer case that is for thecatalyst such that a rectangular upwardly opening end which is on alarge diameter side covers an exhaust gas inflow opening, and extends ina longitudinal direction of said outer case for the catalyst, and adownward-facing opening, which serves as an exhaust gas receiving side,opens onto an edge close to a longitudinal middle portion of said outercase in the exhaust gas inlet pipe, so that an exhaust gas introducingpassage is formed by the outer side surface of an exhaust gas upstreamside outer case and the inner side surface of the exhaust gas inletpipe.
 2. The exhaust gas purification device according to claim 1,wherein a flange body which connects both the outer cases to each otheris deviated from a connection boundary position of both the gaspurification bodies.
 3. The exhaust gas purification device according toclaim 1, wherein the exhaust gas inflow opening which is incommunication with the exhaust gas inlet pipe is formed in the exhaustgas upstream side outer case and the inner case which is incorporated inthis outer case, the exhaust gas inflow opening opens in a rectangularshape, and four corners of the exhaust gas inflow opening are formedinto arc shapes.
 4. The exhaust gas purification device according toclaim 1, wherein a silencer having the exhaust gas outlet pipe ismounted on an exhaust gas downstream side outer case, an exhaust gasintroducing pipe extending in parallel to the exhaust gas movingdirection is incorporated in the silencer, and an exhaust gas upstreamside of the exhaust gas introducing pipe enters an exhaust gasdownstream side inner case.
 5. The exhaust gas purification deviceaccording to claim 4, wherein a flange body which connects both theouter cases to each other is deviated from a connection boundaryposition of both the gas purification bodies, and a flange body whichconnects the exhaust gas downstream side outer case and the silencer toeach other is deviated from a connection boundary position of theexhaust gas downstream side gas purification body.
 6. The exhaust gaspurification device according to claim 4, wherein an exhaust gasupstream side end of the silencer is closed by an inner lid body, theexhaust gas introducing pipe penetrates the inner lid body and entersthe exhaust gas downstream side inner case, and a communication hole fortaking exhaust gas in is formed in a portion of the exhaust gasintroducing pipe on exhaust gas upstream side of the inner lid body. 7.The exhaust gas purification device according to claim 4, wherein asensor boss body for supporting an exhaust gas sensor is provided on aportion of an outer peripheral surface of the exhaust gas downstreamside inner case which is near a connection boundary position of the gaspurification body such that the sensor boss body penetrates the exhaustgas downstream side outer case, and the sensor boss body is located onan extension of an end surface of the gas purification body whichintersects with the exhaust gas moving direction, and on an extension ofan exhaust gas upstream side end surface of the exhaust gas introducingpipe.
 8. The exhaust gas purification device according to claim 1,wherein an end of the exhaust gas inlet pipe at the downward-facingopening deviates from the exhaust gas inflow opening toward the exhaustgas downstream side inside the inner cases.
 9. The exhaust gaspurification device according to claim 1, wherein the exhaust gas inletpipe is formed into a semi-cylindrical shape which opens upward, and iswelded and fixed to the outer side surface of the outer case such thatan end of the exhaust gas inlet pipe at the upward-facing opening, whichis on a large diameter side, covers the exhaust gas inflow opening, andextends in a longitudinal direction of the outer case.
 10. An exhaustgas purification device comprising: two gas purification bodies forpurifying exhaust gas discharged from an engine; inner cases forincorporating the gas purification bodies; outer cases for incorporatingthe inner cases, the outer cases being arranged side by side in anexhaust gas moving direction and connected to each other, wherein one ofthe adjoining inner cases is inserted into the other inner case to forma double-layer structure, and a loosely-fitting gap is formed between aninner side surface of the one inner case and an outer side surface ofthe other inner case; and an exhaust gas introducing passage is formedby the outer side surface of the exhaust gas upstream side outer caseand the inner side surface of the exhaust gas inlet pipe, wherein theexhaust gas inlet pipe is mounted on an exhaust as upstream side outercase, a first rectifier is provided on an outer side surface of theexhaust gas upstream side outer case, and a second rectifier is providedon the inner side surface of the exhaust gas inlet pipe, the firstrectifier being located on an exhaust gas upstream side, and the secondrectifier being located on an exhaust gas downstream side.
 11. Anexhaust gas purification device comprising: two gas purification bodiesfor purifying exhaust gas discharged from an engine; inner cases forincorporating the gas purification bodies; outer cases for incorporatingthe inner cases, the outer cases being arranged side by side in anexhaust gas moving direction and connected to each other, wherein one ofthe adjoining inner cases is inserted into the other inner case to forma double-layer structure, and a loosely-fitting gap is formed between aninner side surface of the one inner case and an outer side surface ofthe other inner case; and an exhaust gas inlet pipe for exhaust gas fromthe engine flowing into, and an exhaust gas outlet pipe for exhaust gaspassing through the gas purification body flowing out, wherein theexhaust gas inlet pipe is mounted on an exhaust gas upstream side outercase such that an exhaust gas introducing passage is formed by the outerside surface of the exhaust gas upstream side outer case and the innerside surface of the exhaust gas inlet pipe, and at least one of theouter side surface of the exhaust gas upstream side outer case and theinner side surface of the exhaust gas inlet pipe is provided with arectifier which rectifies a flow of exhaust gas, and wherein therectifier is provided on each of the outer side surface of the exhaustgas upstream side outer case and the inner side surface of the exhaustgas inlet pipe, the rectifier of the outer case is located on an exhaustgas upstream side, and the rectifier of the exhaust gas inlet pipe islocated on an exhaust gas downstream side.